(x+2)(x-1)=165

Solution for (x+2)(x-1)=165 equation:

(x+2)(x-1)=165

We move all terms to the left:

(x+2)(x-1)-(165)=0

We multiply parentheses ..

(+x^2-1x+2x-2)-165=0

We get rid of parentheses

x^2-1x+2x-2-165=0

We add all the numbers together, and all the variables

x^2+x-167=0

a = 1; b = 1; c = -167;
Δ = b2-4ac
Δ = 12-4·1·(-167)
Δ = 669
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{669}}{2*1}=\frac{-1-\sqrt{669}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{669}}{2*1}=\frac{-1+\sqrt{669}}{2}
$