5y^2+21y+16=0

Solution for 5y^2+21y+16=0 equation:

5y^2+21y+16=0

a = 5; b = 21; c = +16;
Δ = b2-4ac
Δ = 212-4·5·16
Δ = 121
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{121}=11$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-11}{2*5}=\frac{-32}{10}
=-3+1/5
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+11}{2*5}=\frac{-10}{10}
=-1
$