PSAT Math : Polynomials

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:

\(\displaystyle 60\)

\(\displaystyle 18\)

\(\displaystyle 12\)

\(\displaystyle 777\)

\(\displaystyle 837\)

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 #2 : How To Find The Degree Of A Polynomial

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:

\(\displaystyle 70\)

\(\displaystyle 25\)

\(\displaystyle 80\)

\(\displaystyle 100\)

\(\displaystyle 365\)

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:

\(\displaystyle 100\)

\(\displaystyle 154\)

\(\displaystyle 44\)

\(\displaystyle 4\)

\(\displaystyle 174\)

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 #2 : Polynomials

Give the degree of the polynomial

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

Possible Answers:

\(\displaystyle 200\)

\(\displaystyle 100\)

\(\displaystyle 40\)

\(\displaystyle 10\)

\(\displaystyle 400\)

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 #5 : How To Find The Degree Of A Polynomial

Which of these polynomials has the greatest degree?

Possible Answers:

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

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

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

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

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

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 #6 : How To Find The Degree Of A Polynomial

Which of the following monomials has degree 999?

Possible Answers:

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

None of the other responses is correct.

\(\displaystyle 444x^{999}yz\)

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

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

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 #1 : How To Find The Degree Of A Polynomial

Find the degree of the polynomial

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

Possible Answers:

\(\displaystyle \small 4\)

\(\displaystyle \small 5\)

\(\displaystyle 6\)

\(\displaystyle \small 3\)

None of the other answers

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 #3 : Polynomials

Add the polynomials.

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

Possible Answers:

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

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

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

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

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 #21 : Algebra

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

Possible Answers:

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

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

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

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

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

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 #381 : Algebra

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

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

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

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

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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