(x-2)*(x-6)=25

Solution for (x-2)*(x-6)=25 equation:

(x-2)(x-6)=25

We move all terms to the left:

(x-2)(x-6)-(25)=0

We multiply parentheses ..

(+x^2-6x-2x+12)-25=0

We get rid of parentheses

x^2-6x-2x+12-25=0

We add all the numbers together, and all the variables

x^2-8x-13=0

a = 1; b = -8; c = -13;
Δ = b2-4ac
Δ = -82-4·1·(-13)
Δ = 116
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:

$\sqrt{\Delta}=\sqrt{116}=\sqrt{4*29}=\sqrt{4}*\sqrt{29}=2\sqrt{29}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-2\sqrt{29}}{2*1}=\frac{8-2\sqrt{29}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+2\sqrt{29}}{2*1}=\frac{8+2\sqrt{29}}{2}
$