-2x(x+3)=-40

Solution for -2x(x+3)=-40 equation:

-2x(x+3)=-40

We move all terms to the left:

-2x(x+3)-(-40)=0

We add all the numbers together, and all the variables

-2x(x+3)+40=0

We multiply parentheses

-2x^2-6x+40=0

a = -2; b = -6; c = +40;
Δ = b2-4ac
Δ = -62-4·(-2)·40
Δ = 356
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:

$\sqrt{\Delta}=\sqrt{356}=\sqrt{4*89}=\sqrt{4}*\sqrt{89}=2\sqrt{89}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-2\sqrt{89}}{2*-2}=\frac{6-2\sqrt{89}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+2\sqrt{89}}{2*-2}=\frac{6+2\sqrt{89}}{-4}
$