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

Solution for (2-y)(2y+9)=0 equation:

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

We add all the numbers together, and all the variables

(-1y+2)(2y+9)=0

We multiply parentheses ..

(-2y^2-9y+4y+18)=0

We get rid of parentheses

-2y^2-9y+4y+18=0

We add all the numbers together, and all the variables

-2y^2-5y+18=0

a = -2; b = -5; c = +18;
Δ = b2-4ac
Δ = -52-4·(-2)·18
Δ = 169
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{169}=13$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-13}{2*-2}=\frac{-8}{-4}
=+2
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+13}{2*-2}=\frac{18}{-4}
=-4+1/2
$