Functions # MCQs Practice set

Q.1 What is the domain of the function f(x) = 1/x?

All real numbers
All real numbers except 0
x > 0
x < 0
Explanation - The function f(x) = 1/x is undefined at x = 0, so the domain excludes 0.
Correct answer is: All real numbers except 0

Q.2 If f(x) = 2x + 3, what is f(4)?

8
10
11
12
Explanation - Substituting x = 4: f(4) = 2(4) + 3 = 11.
Correct answer is: 11

Q.3 Which of the following is a quadratic function?

f(x) = x + 2
f(x) = x^2 + 3x + 1
f(x) = 1/x
f(x) = √x
Explanation - A quadratic function is a polynomial of degree 2, so f(x) = x^2 + 3x + 1 fits the definition.
Correct answer is: f(x) = x^2 + 3x + 1

Q.4 If f(x) = x^2 and g(x) = x + 1, what is (f ∘ g)(2)?

3
4
9
16
Explanation - (f ∘ g)(2) = f(g(2)) = f(3) = 3^2 = 9.
Correct answer is: 9

Q.5 The graph of y = f(x) = x^2 is symmetric about which axis?

x-axis
y-axis
y = x
origin
Explanation - The parabola y = x^2 is symmetric about the y-axis.
Correct answer is: y-axis

Q.6 If f(x) = 2x - 5, what value of x makes f(x) = 9?

2
5
6
7
Explanation - Solve 2x - 5 = 9 → 2x = 14 → x = 7.
Correct answer is: 7

Q.7 The range of f(x) = x^2 for real numbers is:

All real numbers
x ≥ 0
x > 0
x ≤ 0
Explanation - Squaring any real number yields a non-negative result, so the range is x ≥ 0.
Correct answer is: x ≥ 0

Q.8 Which of the following is NOT a function?

y = x^2
y = |x|
x = y^2
y = 3x + 1
Explanation - x = y^2 fails the vertical line test since for each x there can be two values of y.
Correct answer is: x = y^2

Q.9 If f(x) = 3x and g(x) = x + 2, what is (f ∘ g)(x)?

3x + 2
3x + 6
3x - 2
3x^2 + 2
Explanation - (f ∘ g)(x) = f(g(x)) = f(x+2) = 3(x+2) = 3x + 6.
Correct answer is: 3x + 6

Q.10 The function f(x) = √(x-1) is defined for:

x > 1
x ≥ 1
x < 1
All real x
Explanation - The square root requires a non-negative input, so x - 1 ≥ 0 → x ≥ 1.
Correct answer is: x ≥ 1

Q.11 If f(x) = x^2 - 4, what are the zeros of f(x)?

±2
±4
0 and 4
0 and -4
Explanation - Solve x^2 - 4 = 0 → x^2 = 4 → x = ±2.
Correct answer is: ±2

Q.12 If f(x) = 2x^2 and g(x) = x + 3, what is (g ∘ f)(2)?

5
7
11
11
Explanation - (g ∘ f)(2) = g(f(2)) = g(8) = 8 + 3 = 11.
Correct answer is: 11

Q.13 Which of these functions is linear?

f(x) = x^2 + 1
f(x) = 3x - 7
f(x) = √x
f(x) = 1/x
Explanation - A linear function has the form f(x) = mx + b, which matches f(x) = 3x - 7.
Correct answer is: f(x) = 3x - 7

Q.14 If f(x) = x^3, what is f(-2)?

-6
-8
6
8
Explanation - f(-2) = (-2)^3 = -8.
Correct answer is: -8

Q.15 Which of the following is the inverse of f(x) = 2x + 1?

f⁻¹(x) = x/2 + 1
f⁻¹(x) = (x - 1)/2
f⁻¹(x) = 2x - 1
f⁻¹(x) = x - 2
Explanation - To find the inverse, swap x and y: y = 2x + 1 → x = 2y + 1 → y = (x - 1)/2.
Correct answer is: f⁻¹(x) = (x - 1)/2

Q.16 If f(x) = |x|, what is f(-5)?

-5
0
5
Undefined
Explanation - Absolute value makes all inputs non-negative, so f(-5) = 5.
Correct answer is: 5

Q.17 The graph of f(x) = -x^2 opens:

Upward
Downward
Sideways
Not a parabola
Explanation - The negative coefficient of x^2 makes the parabola open downward.
Correct answer is: Downward

Q.18 If f(x) = 3x + 2, what is f⁻¹(x)?

(x - 2)/3
(x + 2)/3
3x - 2
1/(3x + 2)
Explanation - To find the inverse: y = 3x + 2 → x = 3y + 2 → y = (x - 2)/3.
Correct answer is: (x - 2)/3

Q.19 If f(x) = 2x, what is f(f(x))?

2x
4x
x^2
2x^2
Explanation - f(f(x)) = f(2x) = 2(2x) = 4x.
Correct answer is: 4x

Q.20 The vertex of y = (x - 2)^2 + 3 is:

(0,0)
(2,3)
(-2,3)
(3,2)
Explanation - The vertex form y = (x-h)^2 + k has vertex (h,k), so (2,3).
Correct answer is: (2,3)

Q.21 If f(x) = 1/x, what is f(1/2)?

1/2
2
-2
0
Explanation - f(1/2) = 1/(1/2) = 2.
Correct answer is: 2

Q.22 The graph of f(x) = |x| has shape of:

Parabola
V-shape
Straight line
Circle
Explanation - Absolute value functions graph into a V-shape.
Correct answer is: V-shape

Q.23 If f(x) = x^2 + 2x + 1, what is f(-1)?

0
1
2
3
Explanation - f(-1) = (-1)^2 + 2(-1) + 1 = 1 - 2 + 1 = 0.
Correct answer is: 0

Q.24 If f(x) = x^2 and g(x) = √x, what is (f ∘ g)(9)?

3
9
81
Undefined
Explanation - (f ∘ g)(9) = f(g(9)) = f(√9) = f(3) = 9.
Correct answer is: 9