7y^2-30y-72=0

Solution for 7y^2-30y-72=0 equation:

7y^2-30y-72=0

a = 7; b = -30; c = -72;
Δ = b2-4ac
Δ = -302-4·7·(-72)
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-54}{2*7}=\frac{-24}{14}
=-1+5/7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+54}{2*7}=\frac{84}{14}
=6
$