(7x)(10x+5)=180

Solution for (7x)(10x+5)=180 equation:

(7x)(10x+5)=180

We move all terms to the left:

(7x)(10x+5)-(180)=0

We multiply parentheses

70x^2+35x-180=0

a = 70; b = 35; c = -180;
Δ = b2-4ac
Δ = 352-4·70·(-180)
Δ = 51625
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:

$\sqrt{\Delta}=\sqrt{51625}=\sqrt{25*2065}=\sqrt{25}*\sqrt{2065}=5\sqrt{2065}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(35)-5\sqrt{2065}}{2*70}=\frac{-35-5\sqrt{2065}}{140}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(35)+5\sqrt{2065}}{2*70}=\frac{-35+5\sqrt{2065}}{140}
$