(x-4)(x-1)=990

Solution for (x-4)(x-1)=990 equation:

(x-4)(x-1)=990

We move all terms to the left:

(x-4)(x-1)-(990)=0

We multiply parentheses ..

(+x^2-1x-4x+4)-990=0

We get rid of parentheses

x^2-1x-4x+4-990=0

We add all the numbers together, and all the variables

x^2-5x-986=0

a = 1; b = -5; c = -986;
Δ = b2-4ac
Δ = -52-4·1·(-986)
Δ = 3969
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3969}=63$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-63}{2*1}=\frac{-58}{2}
=-29
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+63}{2*1}=\frac{68}{2}
=34
$