90=(X+2)(5x+35)

Solution for 90=(X+2)(5x+35) equation:

90=(X+2)(5X+35)

We move all terms to the left:

90-((X+2)(5X+35))=0

We multiply parentheses ..

-((+5X^2+35X+10X+70))+90=0


We calculate terms in parentheses: -((+5X^2+35X+10X+70)), so:

(+5X^2+35X+10X+70)

We get rid of parentheses

5X^2+35X+10X+70

We add all the numbers together, and all the variables

5X^2+45X+70

Back to the equation:

-(5X^2+45X+70)


We get rid of parentheses

-5X^2-45X-70+90=0

We add all the numbers together, and all the variables

-5X^2-45X+20=0

a = -5; b = -45; c = +20;
Δ = b2-4ac
Δ = -452-4·(-5)·20
Δ = 2425
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2425}=\sqrt{25*97}=\sqrt{25}*\sqrt{97}=5\sqrt{97}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-45)-5\sqrt{97}}{2*-5}=\frac{45-5\sqrt{97}}{-10}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-45)+5\sqrt{97}}{2*-5}=\frac{45+5\sqrt{97}}{-10}
$