y2=8y+9

Solution for y2=8y+9 equation:

y2=8y+9

We move all terms to the left:

y2-(8y+9)=0

We add all the numbers together, and all the variables

y^2-(8y+9)=0

We get rid of parentheses

y^2-8y-9=0

a = 1; b = -8; c = -9;
Δ = b2-4ac
Δ = -82-4·1·(-9)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-10}{2*1}=\frac{-2}{2}
=-1
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+10}{2*1}=\frac{18}{2}
=9
$