Algebra II : Polynomial Functions

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #1 : How To Find The Degree Of A Polynomial

Give the degree of the polynomial.

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

Possible Answers:

\(\displaystyle 5\)

\(\displaystyle 18\)

\(\displaystyle 7\)

\(\displaystyle 9\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 7\)

Explanation:

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

The degree of an individual term of a polynomial is the exponent of its variable; the exponents of the terms of this polynomial are, in order, 5, 4, 2, and 7.

The degree of the polynomial is the highest degree of any of the terms; in this case, it is 7.

Example Question #1 : How To Find The Degree Of A Polynomial

What is the degree of the polynomial?

\(\displaystyle ab^{2}+a^{2}b^{3}-a^{3}b^{1}\)

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle 4\)

\(\displaystyle 2\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 5\)

Explanation:

\(\displaystyle ab^{2}+a^{2}b^{3}-a^{3}b^{1}\)

To find the degree of the polynomial, you first have to identify each term [term is for example \(\displaystyle ab^{2}\)], so to find the degree of each term you add the exponents.

EX: \(\displaystyle ab^{2}\) \(\displaystyle = a^{1}b^{2} = 1+2= 3\) - Degree of 3

Highest degree is \(\displaystyle 5\rightarrow\) \(\displaystyle a^{2}b^{3}= 2+3= 5\)

Example Question #1 : How To Find The Degree Of A Polynomial

What is the degree of the polynomial?

 \(\displaystyle 12x^2y^3+6xy^4z-2xz+1\)

Possible Answers:

\(\displaystyle 0\)

\(\displaystyle 1\)

\(\displaystyle 6\)

\(\displaystyle 3\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 6\)

Explanation:

To find the degree of the polynomial, add up the exponents of each term and select the highest sum.

12x2y3: 2 + 3 = 5

6xy4z: 1 + 4 + 1 = 6

2xz: 1 + 1 = 2

The degree is therefore 6.

Example Question #1 : Polynomial Functions

Let \(\displaystyle \small f(x)=x^2-10\)\(\displaystyle \small g(x)=x^3\), and \(\displaystyle \small h(x)=2x\). What is \(\displaystyle \small f(h(g(x)))\)?

Possible Answers:

\(\displaystyle \small 4x^6-10\)

\(\displaystyle \small 64x^6-10\)

\(\displaystyle \small 8x^6-240x^4+960x^2-8000\)

\(\displaystyle \small 6x^2-60\)

\(\displaystyle \small \small 2x^6-10\)

Correct answer:

\(\displaystyle \small 4x^6-10\)

Explanation:

When solving functions within functions, we begin with the innermost function and work our way outwards. Therefore:

\(\displaystyle \small h(g(x))=2(x^3)=2x^3\)

and

\(\displaystyle \small f(h(g(x)))=(2x^3)^2-10=4x^6-10\)

Example Question #1 : Polynomial Functions

Let \(\displaystyle \small f(x)=\sqrt[3]{x^2}\)\(\displaystyle \small g(x)=x^3\), and \(\displaystyle \small h(x)=\sqrt[4]{x}\). What is \(\displaystyle \small f(g(h(x)))\)?

Possible Answers:

\(\displaystyle \small \sqrt[4]{x^3}\)

\(\displaystyle \small \sqrt{x}\)

\(\displaystyle \small \sqrt[3]{x^2}\)

\(\displaystyle \small \sqrt[3]{x}\)

\(\displaystyle \small \sqrt[4]{x}\)

Correct answer:

\(\displaystyle \small \sqrt{x}\)

Explanation:

This problem relies on our knowledge of a radical expression \(\displaystyle \small \sqrt[b]{x^a}\) equal to \(\displaystyle \small x^\frac{a}{b}\). The functions are subbed into one another in order from most inner to most outer function.

\(\displaystyle \small g(h(x))=(\sqrt[4]{x})^3=x^\frac{3}{4}\)

and

\(\displaystyle \small f(g(h(x)))=\sqrt[3]{(x^\frac{3}{4})^2}=\sqrt[3]{x^\frac{6}{4}}=x^\frac{6}{12}=x^\frac{1}{2}=\sqrt{x}\)

Example Question #2 : Polynomial Functions

Evaluate \(\displaystyle \small f(g(9))\) if \(\displaystyle \small f(x) = x^2 + 10\) and \(\displaystyle \small g(x) = \sqrt{x^2 -5x+13}\)

Possible Answers:

\(\displaystyle \textup{Undefined}\)

\(\displaystyle 59\)

\(\displaystyle 91\)

\(\displaystyle 7839\)

\(\displaystyle 7\)

Correct answer:

\(\displaystyle 59\)

Explanation:

In problems with functions within one another, we must first solve the innermost function and then proceed outwards. Therefore, the first step is solving \(\displaystyle \small g(9)\) :

 

\(\displaystyle \small g(9) =\small \sqrt{(9)^2 - 5(9)+13}=\sqrt{81-45+13}=\sqrt{49}=\pm7\)

 

Now, we must find the values of \(\displaystyle \small f(\pm 7)\):

\(\displaystyle \small f(\pm 7)= (\pm 7)^2 +10=49+10=59\)

Because our x term is squared in this function, both values end up being the same. Therefore, 59 is our final answer.

Example Question #1 : Polynomial Functions

Evaluate \(\displaystyle \small f(g(-9))\) if \(\displaystyle \small \small f(x)=\sqrt{x^2-4}\) and \(\displaystyle \small g(x)=-\frac{1}{3}x - 2\)

Possible Answers:

\(\displaystyle 21\)

\(\displaystyle 32\)

\(\displaystyle \textup{Undefined}\)

\(\displaystyle \small -\frac{38}{3}\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle \textup{Undefined}\)

Explanation:

Beginning with the innermost function, we must first solve for \(\displaystyle \small \small g(-9)\):

\(\displaystyle \small g(9)=-\frac{1}{3}(-9)-2=3-2=1\)

We then take this value and plug it into \(\displaystyle \small f(x)\):

\(\displaystyle \small f(1)=\sqrt{(1)^2-4}=\sqrt{-3}\)

This has no value in the real number plane, and the answer is therefore undefined.

 

Example Question #2 : Polynomial Functions

\(\displaystyle g(x)=f(-x)\) and \(\displaystyle f(x)=-3x^{2}-7x+4\).

Determine \(\displaystyle g(x)\).

Possible Answers:

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

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

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

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

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

Correct answer:

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

Explanation:

Substituting -x into f(x).  This has no effect on the 1st and 3rd terms.  This changes the sign of the middle term.

Example Question #1 : Polynomial Functions

Which of the following depicts a polynomial in standard form?

Possible Answers:

None of the other answers are correct.

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

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

\(\displaystyle \small 2+6x+x^2+x^4\)

\(\displaystyle \small x^4+x^2+6x-2\)

Correct answer:

\(\displaystyle \small x^4+x^2+6x-2\)

Explanation:

A polynomial in standard form is written in descending order of the power. The highest power should be first, and the lowest power should be last.

\(\displaystyle \small \small x^4+x^2+6x-2\)

The answer has the powers decreasing from four, to two, to one, to zero.

Example Question #2 : Polynomial Functions

 A polynomial consists of one or more terms where each tem has a coefficient and one or more variables raised to a whole number exponent.  A term with an exponent of 0 is a constant.

 

Identify the expression below that is not a polynomial:

  1. \(\displaystyle -10\)
  2. \(\displaystyle 5x\)
  3. \(\displaystyle -2x^{2} +3x\)
  4. \(\displaystyle 3x^{4}-4xy^{2} -10x+5\)
  5. \(\displaystyle -3x^{3} + 2x -3\sqrt{x}-5\)
Possible Answers:

3

1

2

5

4

Correct answer:

5

Explanation:

Expression 5 has the term \(\displaystyle -3\sqrt{x}\), which violates the definition of a polynomial.  The exponent must be a whole number.

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