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

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

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

We add all the numbers together, and all the variables

(4y+9)(-1y+7)=0

We multiply parentheses ..

(-4y^2+28y-9y+63)=0

We get rid of parentheses

-4y^2+28y-9y+63=0

We add all the numbers together, and all the variables

-4y^2+19y+63=0

a = -4; b = 19; c = +63;
Δ = b2-4ac
Δ = 192-4·(-4)·63
Δ = 1369
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1369}=37$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(19)-37}{2*-4}=\frac{-56}{-8}
=+7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(19)+37}{2*-4}=\frac{18}{-8}
=-2+1/4
$