Write in vertex form y = - 4x^2 + 40x+40

Vertex form is y=a (x-h) ²+k

the vertex is (h, k)

complete the square

first, gropu x terms

y = (-4x²+40x) + 40

undistribute quadratic coefient

y=-4 (x²-10x) + 40

take 1/2 of the linear coefinet and square it

-10/2=-5, (-5) ²=25

add positive and negative of it inside the parentahsees

y=-4 (x²-10x+25-25) + 40

factor perfect square trinomial

y=-4 ((x-5) ²-25) + 40

distribute/expand

y=-4 (x-5) ²+100+40

y=-4 (x-5) ²+140

vertex form is y=-4 (x-5) ²+140

the vertex is (5,140)