X(x+25)=90

Solution for X(x+25)=90 equation:

X(X+25)=90

We move all terms to the left:

X(X+25)-(90)=0

We multiply parentheses

X^2+25X-90=0

a = 1; b = 25; c = -90;
Δ = b2-4ac
Δ = 252-4·1·(-90)
Δ = 985
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-\sqrt{985}}{2*1}=\frac{-25-\sqrt{985}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+\sqrt{985}}{2*1}=\frac{-25+\sqrt{985}}{2}
$