Algebra 1 Practice Test: Graphing Quadratic Functions
- Graphing Quadratic Functions
- 10 questions
- 13 minutes
These 10 questions are about the parabola y = ax² + bx + c. The axis of symmetry is x = −b/(2a), and the sign of a tells you whether the parabola opens up or down.
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Question 1
What is the vertex of y = (x − 3)2 + 2?
Correct answer: B
In vertex form y = a(x − h)2 + k the vertex is (h, k). Since x − 3 means h = 3, the vertex is (3, 2), not (−3, 2).
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Question 2
What is the axis of symmetry of y = 2x2 − 8x + 1?
Correct answer: D
Use x = −b2a = −−82 · 2 = 2. Forgetting the factor 2 in the denominator gives 4.
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Question 3
What is the vertex of y = x2 + 6x + 5?
Correct answer: A
The vertex has x = −62 = −3, and y = 9 − 18 + 5 = −4. Using x = 3 comes from dropping the minus sign in −b2a.
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Question 4
Which statement is true about y = −2(x + 1)2 + 5?
Correct answer: C
Since a = −2 is negative, the parabola opens down and its vertex (−1, 5) is the highest point. So the maximum value is the y-coordinate, 5.
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Question 5
What is the y-intercept of y = 3x2 − 4x − 7?
Correct answer: B
At the y-intercept x = 0, so y = 0 − 0 − 7 = −7. The y-intercept of a quadratic in standard form is always c.
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Question 6
What are the x-intercepts of y = x2 − 2x − 8?
Correct answer: D
Set y = 0: (x − 4)(x + 2) = 0, so x = 4 or x = −2. Reading the numbers from the factors without changing the signs gives −4 and 2.
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Question 7
How is the graph of y = −x2 + 4 related to the graph of y = x2?
Correct answer: A
The negative sign in front of x2 reflects the graph over the x-axis, and +4 moves it up 4 units. The width does not change because |a| = 1.
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Question 8
What is the range of y = (x − 1)2 − 3?
Correct answer: C
The parabola opens up and its lowest point is the vertex (1, −3), so every y-value is at least −3. The value 1 is the x-coordinate of the vertex, not a y-value bound.
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Question 9
Which is the vertex form of y = x2 − 4x + 7?
Correct answer: B
Complete the square: x2 − 4x + 4 + 3 = (x − 2)2 + 3. Keeping +7 forgets to subtract the 4 that was added.
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Question 10
A parabola has vertex (1, −8) and passes through (3, 0). Which equation describes it?
Correct answer: A
Start with y = a(x − 1)2 − 8 and substitute (3, 0): 0 = 4a − 8, so a = 2. (x + 1) would put the vertex at x = −1.
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