(x)(x-9)=70

Solution for (x)(x-9)=70 equation:

(x)(x-9)=70

We move all terms to the left:

(x)(x-9)-(70)=0

We multiply parentheses

x^2-9x-70=0

a = 1; b = -9; c = -70;
Δ = b2-4ac
Δ = -92-4·1·(-70)
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-19}{2*1}=\frac{-10}{2}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+19}{2*1}=\frac{28}{2}
=14
$