Question

use the quadratic formula to identify the x-value of the vertex of the equation y=(x-4)(x+2)

Answer 1

Hello:
y=(x-4)(x+2) =x²-2x-8
the quadratic formula   a=1  and b=-2     c=-8
-b/2a =2/2 =1
when x=1   y= 1²-2(1)-8 = -9
the point -vertex is :  A(1 ; -9)