36=-4x^2+40x

Solution for 36=-4x^2+40x equation:

36=-4x^2+40x

We move all terms to the left:

36-(-4x^2+40x)=0

We get rid of parentheses

4x^2-40x+36=0

a = 4; b = -40; c = +36;
Δ = b2-4ac
Δ = -402-4·4·36
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-32}{2*4}=\frac{8}{8}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+32}{2*4}=\frac{72}{8}
=9
$