SAT Mathematics : Using Polynomial Division

Study concepts, example questions & explanations for SAT Mathematics

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Example Questions

Example Question #1 :Using Polynomial Division

By what expression canbe multiplied to yield the product?

Possible Answers:

Correct answer:

Explanation:

Divideby通过设置一个长除法。

Divide the lead term of the dividend,, by that of the divisor,; the result is

Enter that as the first term of the quotient. Multiply this by the divisor:

Subtract this from the dividend. This is shown in the figure below.

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Repeat the process with the new difference:

Screen shot 2020 10 01 at 8.20.24 am

Repeating:

Screen shot 2020 10 01 at 8.21.09 am

The quotient - and the correct response - is.

Example Question #2 :Using Polynomial Division

Divide the polynomialby.

Possible Answers:

Correct answer:

Explanation:

Our first step is to list the coefficients of the polynomials in descending order and carry down the first coefficient.

Screen shot 2020 10 01 at 8.25.38 am

We multiply what's below the line byand place the product on top of the line. We find the sum of this number with the next coefficient and place the sum below the line. We keep repeating these steps until we've reached the last coefficients.

To write the answer, we use the numbers below the line as our new coefficients. The last number is our remainder.

with remainder

This can be rewritten as:

Keep in mind:the highest degree of our new polynomial will always be one less than the degree of the original polynomial.

Example Question #3 :Using Polynomial Division

Divide the polynomialby.

Possible Answers:

Correct answer:

Explanation:

Our first step is to list the coefficients of the polynomials in descending order and carry down the first coefficient.

Screen shot 2020 10 01 at 8.28.01 am

Rememberto place awhen there isn't a coefficient given.

We multiply what's below the line byand place the product on top of the line. We find the sum of this number with the next coefficient and place the sum below the line. We keep repeating these steps until we've reached the last coefficients.

To write the answer, we use the numbers below the line as our new coefficients. The last number is our remainder.

with remainder

This can be rewritten as:


Keep in mind:the highest degree of our new polynomial will always be one less than the degree of the original polynomial.

Example Question #4 :Using Polynomial Division

Use synthetic division to divideby.

Possible Answers:

Remainder

Remainder

Correct answer:

Explanation:

To divide synthetically, we begin by drawing a box. On the inside separated by spaces, we write the coefficients of the terms of our polynomial being divided. On the outside, we write the root that would satisfy our binomial, namely. Leaving a space for another row of numbers, we then draw a line below our row of coefficients.

We then begin dividing by simply carrying our first coefficient (1) down below the line.

We then multiply this 1 by our divisor (3) and write the resulting product (3) below our next coefficient.

We then add the two numbers in that column and write the sum (5) below the line.

We then simply continue the process by multiplying this 5 by our divisor 3 and writing that product in the next column, adding it to the next coefficient, and continuing until we finish the columns.

We then need to translate our bottom row of numbers into the coefficients of our new quotient. Since the first column originally corresponded to our cubic term, it will now correspond to the quadratic term meaning that our 1 can be translated as. Similarly, our second column transitions from quadratic to linear, making our 5 become. Finally, our third column becomes the constant term, meaning 8 simply remains the constant 8. Finally, our former constant column becomes the column for our remainder. However, since we have a 0, we have no remainder and can disregard it.

Putting all of this together gives us a final answer of

Example Question #5 :Using Polynomial Division

Divide using synthetic division:

Possible Answers:

Correct answer:

Explanation:

First, set up the synthetic division problem by lining up the coefficients. There are a couple of different strategies - for this one, we will put a -7 in the top corner and add the columns.

_________________________

The first step is to bring down the first 1. Then multiply what is below the line by the -7 in the box, write it below the next coefficient, and then add the columns:

_________________________

We can interpret this answer as meaning

Example Question #6 :Using Polynomial Division

What is the result whenis divided by?

Possible Answers:

Correct answer:

Explanation:

Our first step is to list the coefficients of the polynomials in descending order and carry down the first coefficient.

Screen shot 2020 10 01 at 8.34.30 am

We multiply what's below the line byand place the product on top of the line. We find the sum of this number with the next coefficient and place the sum below the line. We keep repeating these steps until we've reached the last coefficient.

To write the answer, we use the numbers below the line as our new coefficients. The last number is our remainder.

with reminder

This can be rewritten as:

Example Question #7 :Using Polynomial Division

Which of the following is equivalent to the expression above for?

Possible Answers:

Correct answer:

Explanation:

To answer this question correctly, you need to know the basic method of polynomial division. It works like long division that you learned in elementary school, but instead of dividing numbers with multiple digits, you are dividing polynomials with multiple terms.

The sneaky trick in this question is that the expression提出了与余项第一main quotient term second! This is the opposite of the standard form of such an expression. But it is still technically mathematically correct, since changing the order of the terms in an addition expression does not change its value. The SAT loves to try to confuse students with sneaky but mathematically valid tricks like this. Always be watching out for them!

So the first thing you should do is rearrange the expression in the question into its most natural standard form:.Now you can see that this expression is the result of a polynomial division operation, with 4 as the main quotient and 2 as the remainder.

Now that you see that 4 is the main quotient, you can recognize that it is the result of dividingby,so they must be the first term of the numerator and the first term of the denominator (which we call the divisor). Therefore we can eliminate the wrong answer choicesand,and focus on the remaining answer choices within the numerator. This is actually thehardest part of solving this question. Many students are confused by the order of the terms and mistakenly take 2 as the main quotient and 4 as the remainder. This mistake can lead to the wrong answer choicein particular.

It is important to understand that the remainder term is always a fractional term with the original divisor still present as the denominator of this fractional term as well. What we often think of as “the remainder”, such as 2 in this case, is actually the numerator of this remainder term.

We can also eliminate the wrong answer choicebecause this division operation would produce the value 4 with no remainder. This leaves only thecorrect answer choice,.The divisorgoes into the numeratorfour times, so the main quotient term is 4. We multiplyby 4 to get, the we subtractto get 2. This is our remainder, giving us the remainder term.Thus we have correctly obtained both terms of the original expression in the question,.

Example Question #8 :Using Polynomial Division

Which of the following expressions is equivalent to?

Possible Answers:

Correct answer:

Explanation:

To answer this question correctly, you need to know the basic method of polynomial division. It works like long division that you learned in elementary school, but instead of dividing numbers with multiple digits, you are dividing polynomials with multiple terms.

第一步的多项式除法的过程in this question is fairly straightforward: The first term will be x because that is the result of dividing the first term of the numeratorby the first term of the denominator (the divisor).

The first tricky part occurs when you multiplybyto get, which you must write beneathand subtract.在执行非常小心subtraction steps when solving polynomial division operations!In basic long division of numbers, all the digits are positive, so the subtraction steps are just like normal subtraction. But in polynomial division, the terms can be negative as well as positive, and it is trickier to perform subtraction correctly with negative terms. Therefore, it is a good idea to perform such subtraction steps bychanging allthe signs of the second polynomial and then adding. In this case, that means rather than trying to do the subtraction step, instead you should change all the signs of the second polynomial toand then add:. Then you will get the correct result.Students who make a mistake in this step and get positiveas a result of the subtraction are likely to end up with one of the wrong answer choicesor.

The next step is to bring down the last term of the numerator-2 to make.Now you see that the divisorgoes into this polynomial -1 times, so the next term of the quotient is -1. The whole quotient is now.

Now you have to multiplyby -1 to get, which you must write beneathand subtract. Again, as recommended above, now it is best to change all the sign of the second polynomialtoand then add:.Then you will get the correct result -4. Students who make a mistake in this step may get 0 as a result of the subtraction and select the wrong answer choice.

Now that you have the quotientand the remainder -4, you can see that thecorrect answer choiceis.

Example Question #9 :Using Polynomial Division

Which of the following is equivalent to?

Possible Answers:

Correct answer:

Explanation:

To answer this question correctly, you need to know the basic method of polynomial division. It works like the long division that you learned in elementary school, but instead of dividing numbers with multiple digits, you are dividing polynomials with multiple terms.

第一步的多项式除法的过程in this question is fairly straightforward: The first term will bebecause that is the result of dividing the first term of the numeratorby the first term of the denominator (the divisor).

Next you multiplybyto get, which you must write beneathand subtract. The result of the subtraction is.

Now you have to understand the next step clearly: youcanstill do another polynomial division step and get another term in the quotient. The divisorlooks “bigger” than, but the important thing is that the first terms are the same, so the result of the division is positive 1. Now you have the whole quotient.Students who don’t realize they can get this second term of the quotient may select the wrong answer choice.

Next you have to multiplyby 1 to get, which you must write beneathand subtract. This is a critical key step: You are really doing the subtraction, and so the correct result is -3. Students who make a mistake in this step may get positive 3 as a result and select the wrong answer choice.

Now that you have the quotientand the remainder -3, you can see that the correct answer choice is.

Example Question #10 :Using Polynomial Division

For a polynomial function, the value ofis.Which of the following statements must be true?

Possible Answers:

is a factor of.

The remainder whenis divided byis.

is a factor of.

is a factor of.

Correct answer:

The remainder whenis divided byis.

Explanation:

This question is really testing your understanding of the concept of a factor of a polynomial. A factor of a polynomial is a divisor by which the polynomial isexactly divisible, with no remainder. This concept works in the same manner as it does with regular numbers: a factor of a number is a divisor by which the number is exactly divisible, with no remainder. For example, 5 is a factor of 30, becauseexactly, with no remainder. But 5 is not a factor of 32, becausewith a remainder of 2.

Here is an important concept to understand about factors of polynomials: If for exampleis a factor of, then the value ofmust be 0. This is actually the same connection that you find when you solve a quadratic equation by factoring it: If one of the factors is, then you know thatis a solution of the equation. Well, since you always make the other side of the quadratic equation 0 in order to solve it, what you have really found is that.Another way to describe this is that -1 is an x-intercept of the graph of the function.

Here is the key point about how this concept is related to this question: If you have no information about any values of the polynomial functionthat are equal to 0, then you have no information about any factors of the polynomial function!The only information this question gives us is that.Since we have no way to determine any values ofthat are equal to0, we have no way to determine what any of the factors ofare.By this fact alone, we already know thatall three answer choices that mention a factor ofmust be wrong!!By process of elimination, thecorrect answer choicemust be "The remainder whenis divided byis."

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