(40+x)x=225

Solution for (40+x)x=225 equation:

(40+x)x=225

We move all terms to the left:

(40+x)x-(225)=0

We add all the numbers together, and all the variables

(x+40)x-225=0

We multiply parentheses

x^2+40x-225=0

a = 1; b = 40; c = -225;
Δ = b2-4ac
Δ = 402-4·1·(-225)
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-50}{2*1}=\frac{-90}{2}
=-45
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+50}{2*1}=\frac{10}{2}
=5
$