7x(x+20)=360

Solution for 7x(x+20)=360 equation:

7x(x+20)=360

We move all terms to the left:

7x(x+20)-(360)=0

We multiply parentheses

7x^2+140x-360=0

a = 7; b = 140; c = -360;
Δ = b2-4ac
Δ = 1402-4·7·(-360)
Δ = 29680
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:

$\sqrt{\Delta}=\sqrt{29680}=\sqrt{16*1855}=\sqrt{16}*\sqrt{1855}=4\sqrt{1855}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(140)-4\sqrt{1855}}{2*7}=\frac{-140-4\sqrt{1855}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(140)+4\sqrt{1855}}{2*7}=\frac{-140+4\sqrt{1855}}{14}
$