# Let’s Review Regents: Algebra II Revised Edition by Gary M. Rubenstein – Ebook

January 2019 Geometry Regents Video Answer Key #13-24
January 2019 Geometry Regents Video Answer Key #13-24

Let’s Review Regents: Algebra II Revised Edition

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Features include:

• In-depth Regents exam preparation, including two recent Algebra II Regents exams and answer keys
• Easy to read topic summaries
• Step-by-step demonstrations and examples
• Hundreds of sample questions with fully explained answers for practice and review, and more
• Review of all Algebra II topics, including Polynomial Functions, Exponents and Equations, Transformation of Functions, Trigonometric Functions and their Graphs, Using Sine and Cosine, and much more

Teachers can also use this book to plan lessons and as a helpful resource for practice, homework, and test questions.

Looking for additional practice and review? Check out Barron’s Algebra II Power Pack two-volume set, which includes Regents Exams and Answers: Algebra II in addition to Let’s Review Regents: Algebra II.

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## Preface

In 2009, New York State adopted the Common Core Standards in order to qualify for President Obama’s Race To The Top initiative. The Common Core math curriculum is more difficult than the previous math curriculum. The new state tests, including the Common Core Algebra II Regents, are more difficult as well.

Certain topics that had been in the Algebra II/Trigonometry curriculum for decades have been removed for not being rigorous enough. Other topics have been added with the goal of making 21st-century American students more career and college ready than their predecessors.

The main topics that have been cut from the curriculum are permutations, combinations, Bernoulli trials, binomial expansion, and the majority of the trigonometric identities like the sine sum, cosine sum, sine difference, cosine difference, and the different double-angle and halfangle formulas. Other topics have been moved into earlier grades like the law of sines and the law of cosines. More than half of the trigonometry that had once been part of Algebra II is no longer part of the course.

Other topics have been added to fill the gaps left by those topics now considered obsolete. Primarily, these new topics are often taught in AP Statistics as part of inferential statistics.

Aside from the change in topics, there is a change in the style of questions. Students now need to think more deeply about the topics because questions are intentionally phrased in a less straightforward way than they had been in the past.

Conquering the Algebra II test, something that was never an easy feat beforehand, has gotten much more difficult and will require more test preparation than before. Getting this book is a great first step toward that goal. In addition to reviewing all of the topics that can appear on this test, this book includes nearly 1,000 practice questions of various difficulty levels. This book can serve as a review or even as a way to learn the material for the first time. Teachers can also use this book to guide their pacing. They can focus on the types of questions that are most likely to appear on the test and spend less time on complicated aspects of the Common Core curriculum that are unlikely to be on the test.

The Common Core is part of a grand plan that is intended to propel our country to the top of the international rankings in math and reading. Good luck. We are all counting on you!

Gary Rubinstein

Math Teacher

2016

## Key Ideas

A polynomial is an expression like x² − 5x + 6 that combines numbers and variables raised to different powers. Just as two numbers can be added, subtracted, multiplied, or divided, polynomials can be too.

## Multiplying a Polynomial by a Constant

To multiply a polynomial by a constant, multiply the constant by each of the coefficients of the polynomial. This is sometimes called distributing the constant through the polynomial.

To multiply 3x² − 2x + 5 by 4, multiply each of the coefficients by 4.

To add two polynomials, combine the like terms, which have the same variable raised to the same exponent.

To add the two polynomials (x² − 5x + 6) + (2x² + 3x − 2), first combine the two x²-terms, x² + 2x² = 3x². Then combine the two x-terms, −5x + 3x = −2x. Then combine the two constant terms +6 − 2 = +4. The sum is 3x² − 2x + 4.

## Subtracting Polynomials

Subtracting polynomials is more complicated than adding polynomials.

Since the − sign can be thought of as a negative 1 (−1) and the coefficient of the x² in the second polynomial is really a 1, this can be rewritten as:

Distribute the −1 through the second polynomial. The parentheses are no longer needed.

Combine like terms.

## Multiplying Polynomials

Multiplying two polynomials requires multiplying each combination of one term from the first polynomial with one term from the second polynomial and then combining all the products. The most common type of polynomial multiplication is when each of the polynomials has just two terms (called binomials). The four combinations can then be remembered with the word FOIL.

First terms in each expression: 5x • 2x = +10x²

Outer terms in each expression: 5x • − 4 = −20x

Inner terms in each expression: +3 • 2x = +6x

Last terms in each expression: +3 • −4 = −12

If one or both of the polynomials has more than two terms, then the FOIL method does not apply. Instead, get all the combinations by multiplying the first term in the polynomial on the left by all the terms in the polynomial on the right. Then multiply the second term in the polynomial on the left by all the terms in the polynomial on the right. Continue until the last term in the polynomial on the left has been multiplied by all the terms in the polynomial on the right.

## Example 1

Multiply (x + 3)(2x² − 4x + 5)

Solution: First multiply the x in the binomial by each of the terms of 2x² − 4x + 5. Then multiply the +3 in the binomial by each of the terms of 2x² − 4x + 5. Combine the like terms.

## Multiplication Patterns

Two useful patterns for multiplying binomials without using FOIL or the combination method are the perfect square multiplying pattern and the difference of perfect squares multiplying pattern.

Simplifying (x + 5)² with FOIL becomes x² + 5x + 5x + (5 • 5) = x² + 10x + 25. The coefficient of the x in the solution is double the +5, whereas the constant in the solution is the square of +5. In general, (x + a)² = x² + 2ax + a².

## Example 2

Use the perfect square multiplying pattern to simplify (x − 3)².

Solution: The coefficient will be 2 • (−3) = −6, and the constant will be (−3)² = +9.

When the only difference between two binomials is that one has a + between the two terms and the other has a − between the two terms, there is a shortcut for multiplying the binomials.

Simplifying (x − 5)(x + 5) with FOIL becomes x² + 5x − 5x − 25 = x² − 25. There is no x-term in the answer, and the constant term is the negative square of the constant term of either of the binomials. In general, (x − a)(x + a) = x² − a².

## Example 3

Use the difference of perfect squares multiplying pattern to simplify:

Solution: Since the only difference between the two binomials is the sign between the two terms, this pattern can be used. The answer is x² − 3² = x² − 9.

## Dividing Polynomials

Dividing polynomials requires a process very similar to long division for numbers.

Step 1:

Set up for the long division process.

Step 2:

Determine what you would need to multiply by the first term of the divisor (x in this example) to get the first term in the dividend (2x³ in this example). Since you would need to multiply x by 2x² to get 2x³, the first term of the solution is 2x². Put that term over the x²-term in the dividend.

Step 3:

Multiply the 2x² by the x + 3 to get 2x³ + 6x. Put that product under the 2x³ + x². Subtract and bring down the −11x.

Step 4:

Determine what you would need to multiply by the first term of the divisor (x in this example) to get the first term in the expression at the bottom (−5x² in this example). Since you would need to multiply x by −5x to get −5x², the second term of the solution is −5x. Put that term over the x-term in the dividend. Multiply the −5x by the x + 3, and put the product under the −5x² − 11x. Then subtract and bring down the +12.

Step 5:

Determine what you would need to multiply by the first term of the divisor (x in this example) to get the first term in the expression at the bottom (4x in this example). Since you would need to multiply x by 4 to get 4x, the third term of the solution is +4. Put that term over the constant term in the dividend. Multiply the +4 by the x + 3, and put the product under the 4x + 2. Then subtract. As there is nothing left to bring down, this final number at the bottom is the remainder. Since the remainder in this example is 0, we sometimes say there is no remainder and that x + 3 divides evenly into 2x³ − x² − 11x + 12.

Step 6:

You can check your answer by multiplying the solution by the divisor and then adding the remainder to see if the result is equal to the dividend.

## Example 4

What is the quotient and remainder (if any) of the following?

3x² + 4x − 2, remainder 5

3x² − 4x + 2, remainder 5

3x² + 4x + 2, remainder 6

3x² − 4x − 2, remainder 6

Solution:

Since Example 4 is a multiple-choice question, an alternative way to do this one would be to check each of the answer choices. Multiply each potential solution by x + 4, and add the potential remainder. The answer choice that gives you 3x³ + 8x² − 14x + 13 is the correct one.

Checking choice (2) would look like:

The other choices all give different results. Admittedly, performing four multiplications to check the four choices might take longer than dividing. If on the test you forget how to divide polynomials and there is a multiple-choice question involving polynomial division, then this method would be a way to get the correct answer.

## Check Your Understanding of Section 1.1

A. Multiple-Choice

What is 5 • (2x² + 7x − 3)?

10x² + 35x − 15

10x² + 7x − 3

2x² + 7x − 15

2x² + 35x − 15

What is (−4) • (2x² + 7x − 3)?

−8x² − 28x − 12

−8x² − 28x + 12

−8x² + 7x − 3

2x² + 7x + 12

What is (3x² − 5x + 7) + (2x² + 3x − 4)?

5x² − 8x + 3

5x⁴ − 2x + 3

5x² − 2x + 11

5x² − 2x + 3

What is (5x² − 3x + 8) − (2x² + 4x − 2)?

3x² − 7x + 10

3x² + x + 10

3x² − 7x + 6

3x² + x + 6

What is 2 • (3x² − 4x + 7) − 3(x² − 2x − 5)?

3x² − 14x − 1

3x² − 14x + 29

3x² − 2x − 1

3x² − 2x + 29

What is (5x − 2)(2x + 7)?

10x² − 14

10x² + 35x − 14

10x² − 4x − 14

10x² + 31x − 14

What is (4x² + 2)(3x − 1)?

12x³ − 4x² + 6x − 2

12x³ − 2

12x² + 4x² − 6x + 2

12x² − 4x² − 6x − 2

What is (x + 2)(3x² + 2x − 7)?

3x³ + 2x − 14

3x³ + 8x² − 3x − 14

3x³ + 8x² + 3x − 14

3x³ − 8x² − 3x − 14

What is (x − 7)²?

x² − 14x + 49

x² − 14x − 49

x² + 49

x² − 49

What is (3x² + 5)²?

9x⁴ + 25

9x⁴ + 15x² + 25

9x⁴ + 15x − 25

9x⁴ + 30x² + 25

What is (x³ + x² − 18x − 3) ÷ (x − 4)?

x² + 5x + 2 R3

x² + 5x + 2 R4

x² + 5x + 2 R5

x² + 5x + 2 R6

Simplify 5 • (2x² − 3x + 4).

Zahra calculated (5x² + 7x +10) − (2x² + 3x + 4) as 5x² + 7x + 10 − 2x² + 3x + 4 and got 3x² + 10x + 14. What mistake did Zahra make?

If (x + 5)(x + a) = x² + 7x + 10, what is the value of a?

If (x + a)² = x² + 10x + 25, what is the value of a?

Simplify (x + 3)³.

## A. Multiple-Choice

1

2

4

1

4

4

1

2

1

4

3

10x² − 15x + 20

Zahra did not distribute the – through. The correct answer is 3x² + 4x + 6.

a = 2

4x² + 10x + 25 is a perfect square trinomial because . It factors to . So a = 5.

x³ + 9x² + 27x + 27

## Key Ideas

Factoring an integer means finding two other integers (other than 1) whose product is equal to the original integer. For example, the integer 15 has the factors 3 and 5 since 3 • 5 = 15. Likewise, a polynomial like x² − 5x + 6 can be factored into (x − 2)(x − 3) because (x − 2)(x − 3) = x² − 5x + 6. When a polynomial is factored, the factors can provide useful information about the polynomial that was not apparent in the nonfactored form.

Just like some numbers can’t be factored (for example, 7 and other prime numbers) some polynomials cannot be factored either. When a polynomial can be factored, there are several different methods of obtaining the factorization, depending on the polynomial.

## Greatest Common Factor Factoring

Greatest common factor factoring is the first type of factoring you should always try. If all the terms of a polynomial have a common factor, that common factor can be

factored out.

Often the only common factor is the number 1, in which case this type of factoring is not useful.

An example of using this method is factoring the polynomial 6x³ − 4x² + 8x. Each term of the polynomial 6x³ − 4x² + 8x has a factor of 2x. When the 2x is factored out, it is generally put on the left side and the remaining factor is put on the right in parentheses.

First write the 2x on the left of the parentheses

Now imagine distributing the 2x through as if you were going to multiply the 2x by what needs to go inside the parentheses. For each term in the expression on the right, think “What does 2x need to be multiplied by to become this?” For the first term, 6x³, you have to multiply 2x by 3x² (2 • 3 = 6, and x • x² = x³). So the first term inside the parentheses is 3x².

Do this for the other two terms to get

## Example 1

Factor the polynomial 8x⁴ − 12x³ + 16x².

Solution: Each of the three terms has a factor of 4x². The factorization is

## Factoring a Quadratic Trinomial into the Product of Two Binomials

What’s the opposite of FOIL? Is it LIOF? No. The opposite is factoring a quadratic trinomial like x² + 5x + 6 into the product of two binomials.

If the trinomial is of the form x² + bx + c = 0, find two numbers that have a sum of b and a product of c. For x² + 5x + 6, the two numbers that have a sum of 5 and a product of 6 are +2 and +3. Those numbers become the constants of the two binomials (x + 2) and (x + 3). So x² + 5x + 6 = (x + 2)(x + 3).

## Example 2

Factor the polynomial x² + 3x − 10 into the product of two binomials.

Solution: The two numbers that have a sum of +3 and a product of −10 are −2 and +5. So the two factors are (x − 2) and (x + 5).

## Perfect Square Trinomial Factoring

The trinomials x² + 6x + 9, x² + 8x + 16, and x² + 10x + 25 are three examples of perfect square trinomials. These can be factored into (x + 3)², (x + 4)², and (x + 5)², respectively. The way to recognize a perfect square trinomial of the form x² + bx + c is to compare c to :

If , the trinomial is a perfect square and can be factored as .

For x² + 6x + 9, since , the trinomial is a perfect square.

It can be factored as .

## Example 3

Which of the following is a perfect square trinomial?

x² + 8x + 25

x² − 18x + 36

x² + 10x − 25

x² − 12x + 36

Solution: Since , choice (4) is a perfect square trinomial. Notice that choice (3) would need to have +25 instead of −25 to be a perfect square trinomial.

## Example 4

Factor x² − 18x + 81.

Solution: Since , the trinomial is a perfect square trinomial. It can be factored as .

## Difference of Perfect Squares Factoring

A quadratic expression like x² − 5² is known as the difference between perfect squares since each of the terms is a perfect square and there is a subtraction sign between the two signs. In general, the expression x² − a² can be factored into (x − a)(x + a). For the example x² − 5², it factors into (x − 5)(x + 5).

## Example 5

Factor x² − 81.

Solution: Since 81 can be written as 9², x² − 81 = x² − 9² = (x − 9)(x + 9).

## Factoring Cubic Expressions by Grouping

Polynomial expressions that have one of the variables raised to the third power are called cubic polynomials. Generally, they are very difficult to factor. Sometimes a technique called factor by grouping can be used to factor certain cubic polynomials.

Factor by grouping is when you have a four-term cubic expression and you factor a common factor from the first two terms and another common factor from the last two terms. Then you cross your fingers and hope that there will be a new common factor that you can then factor out.

For example, the polynomial x³ − 3x² + 4x − 12 can be factored this way.

An x² can be factored out of the first two terms, and a 4 can be factored out of the last two terms.

At this point, notice that both of the terms have a factor of (x − 3). This can be factored out to become (x − 3)(x² + 4) just like factoring an expression like x² • a + 4 • a = a(x² + 4).

## Example 6

Completely factor x³ + 2x² − 9x − 18.

Solution: First factor an x² out of the first two terms.

Now you can factor a −9 out of the second two terms so that the (x + 2) factor matches the other one.

Because the question says to factor

completely,

check to see if any of the expressions can be factored further.

Since x² − 9 is a difference between perfect squares, it can be factored into (x − 3)(x + 3). So the original expression can be completely factored to (x + 2)(x − 3)(x + 3).

## Factoring More Complicated Expressions

Polynomials that have exponents greater than 3 can sometimes be factored by rewriting the polynomials in an equivalent form that can be factored with other methods.

The expression x⁶ − 16 has an exponent of 6. Since 6 is an even number, x⁶ can be expressed as (x³)². Since 16 is a perfect square, the original expression can be written as (x³)² − 4², which can then be factored with the difference of perfect squares pattern: (x³ − 4)(x³ + 4).

The trinomial x⁴ + 5x² − 14 resembles the kind of quadratic trinomial from earlier in this chapter. It can be written as (x²)² + 5(x²) − 14. This looks a lot like u² + 5u − 14. If it were u² + 5u − 14, it would factor into (u + 7)(u − 2). So the original trinomial factors instead into (x² + 7)(x² − 2).

## Example 7

Factor x⁸ + 10x⁴ + 25.

Solution: This can be expressed as (x⁴)² + 10(x⁴) + 25, which looks a lot like u² + 10u + 25. Since u² + 10u + 25 has the perfect square trinomial pattern, , it factors into (u + 5)². So the example factors into (x⁴ + 5)².

## Algebra Identities

When two algebraic expressions can be simplified to the same expression, it is called an identity. Proving that something is an identity requires simplifying one or both sides of the equation until the two sides are identical. Until an identity is proved, there will be a small question mark over the equal sign like . After the identity is established, the question mark over the equals sign is replaced with a check .

## Example 8

Prove the following identity.

Solution:

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