13y^2-18y-90=0

Solution for 13y^2-18y-90=0 equation:

13y^2-18y-90=0

a = 13; b = -18; c = -90;
Δ = b2-4ac
Δ = -182-4·13·(-90)
Δ = 5004
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:

$\sqrt{\Delta}=\sqrt{5004}=\sqrt{36*139}=\sqrt{36}*\sqrt{139}=6\sqrt{139}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-6\sqrt{139}}{2*13}=\frac{18-6\sqrt{139}}{26}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+6\sqrt{139}}{2*13}=\frac{18+6\sqrt{139}}{26}
$