(x-1)*(x+2)=54

Solution for (x-1)*(x+2)=54 equation:

(x-1)(x+2)=54

We move all terms to the left:

(x-1)(x+2)-(54)=0

We multiply parentheses ..

(+x^2+2x-1x-2)-54=0

We get rid of parentheses

x^2+2x-1x-2-54=0

We add all the numbers together, and all the variables

x^2+x-56=0

a = 1; b = 1; c = -56;
Δ = b2-4ac
Δ = 12-4·1·(-56)
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-15}{2*1}=\frac{-16}{2}
=-8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+15}{2*1}=\frac{14}{2}
=7
$