Question

Select the x-coordinate of the vertex of the parabola defined by the function f(x)=-9x^2+7x+8

Answer 1

$f(x)=-9x^2+7x+8\\\\a=-9;\ b=7;\ c=8\\\\x_{vertex}=\frac{-b}{2a}\\\\x_{vertex}=\frac{-7}{2\cdot(-9)}=\frac{-7}{-18}=\frac{7}{18}$

Answer 2

$x_v=-\frac{b}{2a}\\ x_v=-\frac{7}{2\cdot(-9)}\\ x_v=\frac{7}{18}$