(9+y)(4y-7)=0

Solution for (9+y)(4y-7)=0 equation:

(9+y)(4y-7)=0

We add all the numbers together, and all the variables

(y+9)(4y-7)=0

We multiply parentheses ..

(+4y^2-7y+36y-63)=0

We get rid of parentheses

4y^2-7y+36y-63=0

We add all the numbers together, and all the variables

4y^2+29y-63=0

a = 4; b = 29; c = -63;
Δ = b2-4ac
Δ = 292-4·4·(-63)
Δ = 1849
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1849}=43$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(29)-43}{2*4}=\frac{-72}{8}
=-9
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(29)+43}{2*4}=\frac{14}{8}
=1+3/4
$