7y(4y-15)=180

Solution for 7y(4y-15)=180 equation:

7y(4y-15)=180

We move all terms to the left:

7y(4y-15)-(180)=0

We multiply parentheses

28y^2-105y-180=0

a = 28; b = -105; c = -180;
Δ = b2-4ac
Δ = -1052-4·28·(-180)
Δ = 31185
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{31185}=\sqrt{81*385}=\sqrt{81}*\sqrt{385}=9\sqrt{385}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-105)-9\sqrt{385}}{2*28}=\frac{105-9\sqrt{385}}{56}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-105)+9\sqrt{385}}{2*28}=\frac{105+9\sqrt{385}}{56}
$