Question

Select the x-coordinate of the vertex of the parabola defined by the function f(x) = -7x2 + 5x + 9.

-7/5

9

5/14
-5/7

Answer 1

-7x^2+5x+9

= -7(x^2 - 5/7x) - 9
= -7(x^2 - 5/7 x + (5/14)^2) + 7(5/14)^2 - 9
= -7(x - 5/14)^2 + c
for an c = 7(5/14)^2 - 9

Note that the x-coordinate is 5/14