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

Solution for (9+y)(4y-2)=0 equation:

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

(+4y^2-2y+36y-18)=0

We get rid of parentheses

4y^2-2y+36y-18=0

We add all the numbers together, and all the variables

4y^2+34y-18=0

a = 4; b = 34; c = -18;
Δ = b2-4ac
Δ = 342-4·4·(-18)
Δ = 1444
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1444}=38$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(34)-38}{2*4}=\frac{-72}{8}
=-9
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(34)+38}{2*4}=\frac{4}{8}
=1/2
$