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

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

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

(+4y^2-9y+16y-36)=0

We get rid of parentheses

4y^2-9y+16y-36=0

We add all the numbers together, and all the variables

4y^2+7y-36=0

a = 4; b = 7; c = -36;
Δ = b2-4ac
Δ = 72-4·4·(-36)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-25}{2*4}=\frac{-32}{8}
=-4
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+25}{2*4}=\frac{18}{8}
=2+1/4
$