y^2-30y+216=0

Solution for y^2-30y+216=0 equation:

y^2-30y+216=0

a = 1; b = -30; c = +216;
Δ = b2-4ac
Δ = -302-4·1·216
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-6}{2*1}=\frac{24}{2}
=12
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+6}{2*1}=\frac{36}{2}
=18
$