(2x-7)(x+3)=90

Solution for (2x-7)(x+3)=90 equation:

(2x-7)(x+3)=90

We move all terms to the left:

(2x-7)(x+3)-(90)=0

We multiply parentheses ..

(+2x^2+6x-7x-21)-90=0

We get rid of parentheses

2x^2+6x-7x-21-90=0

We add all the numbers together, and all the variables

2x^2-1x-111=0

a = 2; b = -1; c = -111;
Δ = b2-4ac
Δ = -12-4·2·(-111)
Δ = 889
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{889}}{2*2}=\frac{1-\sqrt{889}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{889}}{2*2}=\frac{1+\sqrt{889}}{4}
$