Advanced Math practice question

Answer: -2 or −2

The vertex's x-coordinate is −b/(2a) = −8/(2a) = 2, so 2a = −4 and a = −2. (Then c = 3, since f(2) = −8 + 16 + c = 11.)

Common wrong answers

If you answered 2

2 has the wrong sign; −8/(2a) = 2 gives a negative a.

If you answered 3

3 is c, not a.

If you answered -4

−4 forgets the 2 in the denominator: −8/(2a), not −8/a.

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