GRE Math : Algebraic Functions

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #2791 : Sat Mathematics

If \small f(x) = 4x^{2}+3x+2 and \small g(x) = x+7, what is \small f(g(x))?

Possible Answers:

\small 4x^{2}+59x+219

\small 4x^{2}+3x+72

\small 4x^{2}+17x+219

\small 4x^{2}+3x+219

\small 4x^{2}+17x+72

Correct answer:

\small 4x^{2}+59x+219

Explanation:

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

\small 4(x^{2} + 14x + 49)+ 3x +21 + 2

\small 4x^{2}+56x+196+3x+23

\small 4x^{2}+59x+219

Example Question #23 : Algebraic Functions

If  and , which of the following could represent ?

Possible Answers:

Correct answer:

Explanation:

The number in the parentheses is what goes into the function.

For the function ,

 and

Example Question #2792 : Sat Mathematics

A function F is defined as follows:

for x2 > 1, F(x) = 4x2 + 2x – 2

for x2 < 1, F(x) = 4x2 – 2x + 2

What is the value of F(1/2)?

Possible Answers:

Correct answer:

Explanation:

For F(1/2), x2=1/4, which is less than 1, so we use the bottom equation to solve. This gives F(1/2)= 4(1/2)2 – 2(1/2) + 2 = 1 – 1 + 2 = 2

Example Question #11 : Algebraic Functions

Which of the statements describes the solution set for 7(x + 3) = 7x + 20 ? 

Possible Answers:

There are no solutions.

x = 1

All real numbers are solutions.

x = 0

Correct answer:

There are no solutions.

Explanation:

By distribution we obtain 7x – 21 = – 7x + 20. This equation is never possibly true.

Example Question #12 : Algebraic Functions

Will just joined a poetry writing group in town that meets once a week. The number of poems Will has written after a certain number of meetings can be represented by the function , where  represents the number of meetings Will has attended. Using this function, how many poems has Will written after 7 classes?

Possible Answers:

Correct answer:

Explanation:

For this function, simply plug 7 in for  and solve:

Example Question #13 : Algebraic Functions

If f(x)=x^{2}+3, then f(x+h)= ?

Possible Answers:

x^{2}+h^{2}

x^{2}+2xh+h^{2}

x^{2}+2xh+h^{2}+3

x^{2}+h^{2}+3

x^{2}+3+h

Correct answer:

x^{2}+2xh+h^{2}+3

Explanation:

To find f(x+h) when f(x)=x^{2}+3, we substitute (x+h) for x in f(x).

Thus, f(x+h)=(x+h)^{2}+3.

We expand (x+h)^{2}  to x^{2}+xh+xh+h^{2}.

We can combine like terms to get x^{2}+2xh+h^{2}.

We add 3 to this result to get our final answer.

Example Question #15 : Algebraic Functions

What is the value of the function f(x) = 6x+ 16x – 6 when x = –3?

Possible Answers:

–108

96

–12

0

Correct answer:

0

Explanation:

There are two ways to do this problem. The first way just involves plugging in –3 for x and solving 6〖(–3)〗+ 16(–3) – 6, which equals 54 – 48 – 6 = 0. The second way involves factoring the polynomial to (6x – 2)(x + 3) and then plugging in –3 for x. The second way quickly shows that the answer is 0 due to multiplying by (–3 + 3).

Example Question #14 : Algebraic Functions

Given the functions f(x) = 2x + 4 and g(x) = 3x – 6, what is f(g(x)) when = 6?

Possible Answers:

144

12

28

192

16

Correct answer:

28

Explanation:

We need to work from the inside to the outside, so g(6) = 3(6) – 6 = 12.

Then f(g(6)) = 2(12) + 4 = 28.

Example Question #15 : Algebraic Functions

A function f(x) = –1 for all values of x. Another function g(x) = 3x for all values of x. What is g(f(x)) when x = 4?

Possible Answers:

–1

–3

3

–12

12

Correct answer:

–3

Explanation:

We work from the inside out, so we start with the function f(x). f(4) = –1. Then we plug that value into g(x), so g(f(x)) = 3 * (–1) = –3.

Example Question #17 : Algebraic Functions

What is f(–3) if f(x) = x2 + 5?

Possible Answers:

–4

–14

4

15

14

Correct answer:

14

Explanation:

f(–3) = (–3)2 + 5 = 9 + 5 = 14

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