x^2-5(x)=75

Solution for x^2-5(x)=75 equation:

x^2-5(x)=75

We move all terms to the left:

x^2-5(x)-(75)=0

a = 1; b = -5; c = -75;
Δ = b2-4ac
Δ = -52-4·1·(-75)
Δ = 325
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:

$\sqrt{\Delta}=\sqrt{325}=\sqrt{25*13}=\sqrt{25}*\sqrt{13}=5\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-5\sqrt{13}}{2*1}=\frac{5-5\sqrt{13}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+5\sqrt{13}}{2*1}=\frac{5+5\sqrt{13}}{2}
$