Y(y-7)(y-9)=0

Solution for Y(y-7)(y-9)=0 equation:

(Y-7)(Y-9)=0

We multiply parentheses ..

(+Y^2-9Y-7Y+63)=0

We get rid of parentheses

Y^2-9Y-7Y+63=0

We add all the numbers together, and all the variables

Y^2-16Y+63=0

a = 1; b = -16; c = +63;
Δ = b2-4ac
Δ = -162-4·1·63
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-2}{2*1}=\frac{14}{2}
=7
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+2}{2*1}=\frac{18}{2}
=9
$