All ACT Math Resources
Example Questions
Example Question #32 : Algebraic Functions
What is the value of the function f(x) = 6x2 + 16x – 6 when x = –3?
–12
0
96
–108
0
There are two ways to do this problem. The first way just involves plugging in –3 for x and solving 6〖(–3)〗2 + 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 #33 : Algebraic Functions
Given the functions f(x) = 2x + 4 and g(x) = 3x – 6, what is f(g(x)) when x = 6?
12
192
144
28
16
28
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 #34 : 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?
–3
3
12
–12
–1
–3
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 #35 : Algebraic Functions
What is f(–3) if f(x) = x2 + 5?
15
4
–4
14
–14
14
f(–3) = (–3)2 + 5 = 9 + 5 = 14
Example Question #21 : How To Find F(X)
For all values of x, f(x) = 7x2 – 3, and for all values of y, g(y) = 2y + 9. What is g(f(x))?
14y2 + 3
7y2 – 3
14x2 – 3
2x + 9
14x2 + 3
14x2 + 3
The inner function f(x) is like our y-value that we plug into g(y).
g(f(x)) = 2(7x2 – 3) + 9 = 14x2 – 6 + 9 = 14x2 + 3.
Example Question #36 : Algebraic Functions
Find
Simply plug 6 into the equation and don't forget the absolute value at the end.
absolute value = 67
Example Question #1191 : Algebra
An outpost has the supplies to last 2 people for 14 days. How many days will the supplies last for 7 people?
Supplies are used at the rate of .
Since the total amount of supplies is the same in either case, .
Solve for days to find that the supplies will last for 4 days.
Example Question #1192 : Algebra
Worker can make a trinket in 4 hours, Worker can make a trinket in 2 hours. When they work together, how long will it take them to make a trinket?
The rates are what needs to be added. Rate is , or one trinket every 4 hours. Rate is , one per two hours.
, their combined rate in trinkets per hour.
Now invert the equation to get back to hours per trinket, which is what the question asks for:
Example Question #1193 : Algebra
Quantity A Quantity B
Quantity A is greater
The relationship cannot be determined from the information given.
Quantity A and Quantity B are equal
Quantity B is greater
Quantity A and Quantity B are equal
Since , then we have that
and
.
Thus, the two quantities are equal.
Example Question #1194 : Algebra
If the average of two numbers is and one of the numbers is , what is the other number, in terms of and ?
The average is the sum of the terms divided by the number of terms. Here you have and the other number which you can call . The average of and is . So
Multiply both sides by 2.
Solve for .