-40=4x(x-10)

Solution for -40=4x(x-10) equation:

-40=4x(x-10)

We move all terms to the left:

-40-(4x(x-10))=0


We calculate terms in parentheses: -(4x(x-10)), so:

4x(x-10)

We multiply parentheses

4x^2-40x

Back to the equation:

-(4x^2-40x)


We get rid of parentheses

-4x^2+40x-40=0

a = -4; b = 40; c = -40;
Δ = b2-4ac
Δ = 402-4·(-4)·(-40)
Δ = 960
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{960}=\sqrt{64*15}=\sqrt{64}*\sqrt{15}=8\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-8\sqrt{15}}{2*-4}=\frac{-40-8\sqrt{15}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+8\sqrt{15}}{2*-4}=\frac{-40+8\sqrt{15}}{-8}
$