(x-1)(x-1)=225

Solution for (x-1)(x-1)=225 equation:

(x-1)(x-1)=225

We move all terms to the left:

(x-1)(x-1)-(225)=0

We multiply parentheses ..

(+x^2-1x-1x+1)-225=0

We get rid of parentheses

x^2-1x-1x+1-225=0

We add all the numbers together, and all the variables

x^2-2x-224=0

a = 1; b = -2; c = -224;
Δ = b2-4ac
Δ = -22-4·1·(-224)
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-30}{2*1}=\frac{-28}{2}
=-14
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+30}{2*1}=\frac{32}{2}
=16
$