X(5+x)=750

Solution for X(5+x)=750 equation:

X(5+X)=750

We move all terms to the left:

X(5+X)-(750)=0

We add all the numbers together, and all the variables

X(X+5)-750=0

We multiply parentheses

X^2+5X-750=0

a = 1; b = 5; c = -750;
Δ = b2-4ac
Δ = 52-4·1·(-750)
Δ = 3025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3025}=55$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-55}{2*1}=\frac{-60}{2}
=-30
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+55}{2*1}=\frac{50}{2}
=25
$