9y2+20y-16=0

Solution for 9y2+20y-16=0 equation:

9y^2+20y-16=0

a = 9; b = 20; c = -16;
Δ = b2-4ac
Δ = 202-4·9·(-16)
Δ = 976
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:

$\sqrt{\Delta}=\sqrt{976}=\sqrt{16*61}=\sqrt{16}*\sqrt{61}=4\sqrt{61}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-4\sqrt{61}}{2*9}=\frac{-20-4\sqrt{61}}{18}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+4\sqrt{61}}{2*9}=\frac{-20+4\sqrt{61}}{18}
$