PSAT Math : Polynomial Operations

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #11 : Algebra

Give the degree of the polynomial

\displaystyle 777a^{12}b^{14}c^{16}d^{18}

Possible Answers:

\displaystyle 60

\displaystyle 777

\displaystyle 12

\displaystyle 18

\displaystyle 837

Correct answer:

\displaystyle 60

Explanation:

The polynomial has one term, so its degree is the sum of the exponents of the variables:

\displaystyle 12+14 + 16+18 =60

Example Question #1 : Polynomials

Give the degree of the polynomial

\displaystyle x^{50}y^{30} - x^{70}y^{25}+ x^{45}y ^{45} - x^{30}y ^{70}

Possible Answers:

\displaystyle 70

\displaystyle 100

\displaystyle 25

\displaystyle 365

\displaystyle 80

Correct answer:

\displaystyle 100

Explanation:

The degree of a polynomial in more than one variable is the greatest degree of any of the terms; the degree of a term is the sum of the exponents. The degrees of the terms in the given polynomial are:

\displaystyle 50 + 30 = 80

\displaystyle 70 + 25= 95

\displaystyle 45+45 = 90

\displaystyle 30 + 70 = 100

The degree of the polynomial is the greatest of these degrees, 100.

Example Question #1 : Polynomials

Give the degree of the polynomial

\displaystyle y^{44} + y^{20} - y^{10} + y^{100}

Possible Answers:

\displaystyle 174

\displaystyle 100

\displaystyle 4

\displaystyle 44

\displaystyle 154

Correct answer:

\displaystyle 100

Explanation:

The degree of a polynomial in one variable is the greatest exponent of any of the powers of the variable. The terms have as their exponents, in order, 44, 20, 10, and 100; the greatest of these is 100, which is the degree.

Example Question #11 : Algebra

Give the degree of the polynomial

\displaystyle 400x^{10}- 300x^{20} + 200x^{30}-100 x^{40}

Possible Answers:

\displaystyle 400

\displaystyle 200

\displaystyle 100

\displaystyle 40

\displaystyle 10

Correct answer:

\displaystyle 40

Explanation:

The degree of a polynomial in one variable is the greatest exponent of any of the powers of the variable. The terms have as their exponents, in order, 10, 20, 30, and 40; 40 is the greatest of them and is the degree of the polynomial.

Example Question #2 : How To Find The Degree Of A Polynomial

Which of these polynomials has the greatest degree?

Possible Answers:

\displaystyle 7xy^{4} - 4x^{2}+ y^{3}

\displaystyle -5 x^{2}y^{2}+ 7x^{3}y^{2}+ 8x

\displaystyle 8x ^{4}y - 4 y^{2} + 9x^{3}y

All of the polynomials given in the other responses have the same degree.

\displaystyle 6x^{3}y^{2} + 4 xy^{3} - 100

Correct answer:

All of the polynomials given in the other responses have the same degree.

Explanation:

The degree of a polynomial is the highest degree of any term; the degree of a term is the exponent of its variable or the sum of the exponents of its variables, with unwritten exponents being equal to 1. For each term in a polynomial, write the exponent or add the exponents; the greatest number is its degree. We do this with all four choices:

 

\displaystyle \underline{6x^{3}y^{2} + 4 xy^{3} - 100}:

\displaystyle 6x^{3}y^{2}: 3 + 2 = 5

\displaystyle 4 xy^{3}: 1 + 3 = 4

\displaystyle 100: A constant term has degree 0.

The degree of this polynomial is 5.

 

\displaystyle \underline{7xy^{4} - 4x^{2}+ y^{3}}

\displaystyle 7xy^{4} : 1 + 4 = 5

\displaystyle 4x^{2} : 2

\displaystyle y^{3}: 3

The degree of this polynomial is 5.

 

\displaystyle \underline{8x ^{4}y - 4 y^{2} + 9x^{3}y}

\displaystyle 8x ^{4}y: 4 + 1= 5

\displaystyle 4 y^{2} : 2

\displaystyle 9x^{3}y: 3 + 1= 4

The degree of this polynomial is 5.

 

\displaystyle \underline{-5 x^{2}y^{2}+ 7x^{3}y^{2}+ 8x}

\displaystyle -5 x^{2}y^{2} : 2 + 2 = 4

\displaystyle 7x^{3}y^{2} : 3 + 2 = 5

\displaystyle 8x: 1

The degree of this polynomial is 5.

 

All four polynomials have the same degree.

Example Question #21 : Variables

Which of the following monomials has degree 999?

Possible Answers:

\displaystyle 444x^{999}yz

\displaystyle 333x^{999}y^{999}z^{999}

\displaystyle 999x^{4}y^{5}z^{6}

None of the other responses is correct.

\displaystyle 100x^{333}y^{333}z^{333}

Correct answer:

\displaystyle 100x^{333}y^{333}z^{333}

Explanation:

The degree of a monomial term is the sum of the exponents of its variables, with the default being 1.

For each monomial, this sum - and the degree - is as follows:

 

\displaystyle 444x^{999}yz\displaystyle 999 + 1 + 1 = 1,001

\displaystyle 333x^{999}y^{999}z^{999}\displaystyle 999+999+999 = 2,997

\displaystyle 999x^{4}y^{5}z^{6}\displaystyle 4+5+6 = 15 (note - 999 is the coefficient)

\displaystyle 100x^{333}y^{333}z^{333}\displaystyle 333+333+333 = 999

 

\displaystyle 100x^{333}y^{333}z^{333} is the correct choice.

Example Question #22 : Variables

Find the degree of the polynomial

\displaystyle \small - x^{2}+3x - 2x^{5} - x^{3} +4

Possible Answers:

\displaystyle \small 3

None of the other answers

\displaystyle \small 4

\displaystyle 6

\displaystyle \small 5

Correct answer:

\displaystyle \small 5

Explanation:

The degree of the polynomial is the largest degree of any one of it's individual terms.

\displaystyle \small - x^{2}+3x - 2x^{5} - x^{3} +4

The degree of \displaystyle \small -x^2 is \displaystyle \small 2

The degree of  \displaystyle \small 3x is \displaystyle \small 1

The degree of \displaystyle \small -2x^5 is \displaystyle \small 5

The degree of \displaystyle \small -x^3 is \displaystyle \small 3

The degree of  \displaystyle \small 4 is \displaystyle \small 0

\displaystyle \small 5 is the largest degree of any one of the terms of the polynomial, and so the degree of the polynomial is \displaystyle \small 5.

Example Question #21 : Variables

Add the polynomials.

\displaystyle (x^{2}+5x+12) + (3x^{3}+3x+8)

Possible Answers:

\displaystyle 4x^{2}+8x+20

\displaystyle 3x^{3}+x^{2}+6x+17

\displaystyle 4x^{3}+2x^{2}+4x+14

\displaystyle 3x^{3}+x^{2}+8x+20

Correct answer:

\displaystyle 3x^{3}+x^{2}+8x+20

Explanation:

We can add together each of the terms of the polynomial which have the same degree for our variable. \displaystyle (3x^{3}) + (x^{2}) + (5x+3x) + (12+8) = 3x^{3}+x^{2}+8x+20

Example Question #1 : Polynomial Operations

\displaystyle (x^4+7x^2-5x+4)-(-4x^4+5x^3-x^2+3)

Possible Answers:

\displaystyle x^4+7x^2-10x+1

\displaystyle 5x^4-5x^3+8x^2-5x+1

\displaystyle x^4-5x^3+11x^2-5x+1

\displaystyle 5x^4+5x^3+6x^2-5x+7

\displaystyle -3x^4+5x^3+6x^2-5x+7

Correct answer:

\displaystyle 5x^4-5x^3+8x^2-5x+1

Explanation:

Step 1: Distribute the negative to the second polynomial:

\displaystyle (x^4+7x^2-5x+4)-(-4x^4+5x^3-x^2+3)

\displaystyle x^4+7x^2-5x+4+4x^2-5x^3+x^2-3

Step 2: Combine like terms:

\displaystyle x^4+4x^4-5x^3+7x^2+x^2-5x+4-3

\displaystyle 5x^4-5x^3+8x^2-5x+1

Example Question #1 : Polynomial Operations

F(x) = x^{3} + x^{2} - x + 2\displaystyle F(x) = x^{3} + x^{2} - x + 2 

and

G(x) = x^{2} + 5\displaystyle G(x) = x^{2} + 5  

What is \displaystyle FG(x)?

Possible Answers:

(FG)(x) = x^{5} + x^{4} +4x^{3} + 7x^{2} - 5x +10\displaystyle (FG)(x) = x^{5} + x^{4} +4x^{3} + 7x^{2} - 5x +10

(FG)(x) = x^{5} + x^{4} - x - 2\displaystyle (FG)(x) = x^{5} + x^{4} - x - 2

(FG)(x) = x^{3} + 2x^{2} - x + 7\displaystyle (FG)(x) = x^{3} + 2x^{2} - x + 7

(FG)(x) = x^{3} - x - 3\displaystyle (FG)(x) = x^{3} - x - 3

(FG)(x) = x^{5} + x^{4} - x^{3} + 2x^{2} - 5x -10\displaystyle (FG)(x) = x^{5} + x^{4} - x^{3} + 2x^{2} - 5x -10

Correct answer:

(FG)(x) = x^{5} + x^{4} +4x^{3} + 7x^{2} - 5x +10\displaystyle (FG)(x) = x^{5} + x^{4} +4x^{3} + 7x^{2} - 5x +10

Explanation:

(FG)(x) = F(x)G(x)\displaystyle (FG)(x) = F(x)G(x) so we multiply the two function to get the answer.  We use x^{m}x^{n} = x^{m+n}\displaystyle x^{m}x^{n} = x^{m+n}

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