-15y^2+70y-75=0

Solution for -15y^2+70y-75=0 equation:

-15y^2+70y-75=0

a = -15; b = 70; c = -75;
Δ = b2-4ac
Δ = 702-4·(-15)·(-75)
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(70)-20}{2*-15}=\frac{-90}{-30}
=+3
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(70)+20}{2*-15}=\frac{-50}{-30}
=1+2/3
$