Advanced Math practice question

Answer: A. (−2, −5)

The vertex's x-coordinate is −b/(2a) = −4/2 = −2. Substitute to find y: (−2)² + 4(−2) − 1 = 4 − 8 − 1 = −5. The vertex is (−2, −5). (Or complete the square: (x + 2)² − 5.)

Why the other answers are wrong

B. (2, −5)

The sign of the x-coordinate is wrong: −b/(2a) with b = 4 is −2, not 2.

C. (−2, 3)

The y-value was computed with a sign slip: 4 − 8 − 1 is −5, not 3.

D. (−4, −1)

−4 is −b, without dividing by 2a. And −1 is the y-intercept, not the vertex's y-value.

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