How do you find the vertex of a parabola y=(-x-1)(x+7)y=(x1)(x+7)?

1 Answer
Apr 2, 2018

Vertex is at (-4,9) (4,9)

Explanation:

y=(-x-1)(x+7) or y= -(x+1)(x+7)y=(x1)(x+7)ory=(x+1)(x+7) or

y= -(x^2+8x+7) or y= -(x^2+8x)-7y=(x2+8x+7)ory=(x2+8x)7 or

y= -(x^2+8x+16)+16-7y=(x2+8x+16)+167 or

y= -(x+4)^2+9y=(x+4)2+9. Comparing with vertex form of

equation y = a(x-h)^2+k ; (h,k)y=a(xh)2+k;(h,k) being vertex we find

here h=-4 , k=9 :. Vertex is at (-4,9)

graph{(-x-1)(x+7) [-25.32, 25.3, -12.66, 12.66]} [Ans]