y2+21y=0

Solution for y2+21y=0 equation:

y2+21y=0

We add all the numbers together, and all the variables

y^2+21y=0

a = 1; b = 21; c = 0;
Δ = b2-4ac
Δ = 212-4·1·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-21}{2*1}=\frac{-42}{2}
=-21
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+21}{2*1}=\frac{0}{2}
=0
$