7

Set 6: Quadratic Equations (Intermediate)

Explanation

Answer: A

What are the coordinates of the vertex for y=2x2+8x3y = 2x^2 + 8x - 3?

A.

(2,11)(-2, -11)

✓ Correct
B.

(2,21)(2, 21)

C.

(2,3)(-2, -3)

D.

(4,3)(-4, -3)

Detailed Explanation

Choice A is correct. Choice A is the correct answer. The vertex (h,k)(h, k) is found by first calculating the x-coordinate h=b/2ah = -b/2 a. 1. h=8/(2×2)=8/4=2h = -8 / (2 \times 2) = -8 / 4 = -2. 2. Substitute x=2x = -2 back into the equation to find yy: y=2(2)2+8(2)3y = 2(-2)^2 + 8(-2) - 3 y=2(4)163y = 2(4) - 16 - 3 y=8163=11y = 8 - 16 - 3 = -11. So the vertex is (2,11)(-2, -11). Choice B is incorrect because it uses x=2x=2. Choice C is incorrect because it assumes the y-intercept (-3) is the y-coordinate of the vertex. Choice D is incorrect because it calculates x incorrectly.

Key Steps:

The correct answer is (2,11)(-2, -11)

Why others are wrong:
B: Choice B is incorrect and may result from a calculation error.
C: Choice C is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

🎯 Keep Practicing!

Master all sections for your best SAT score