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

Solution for (7-y)(2y+9)=0 equation:

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

We add all the numbers together, and all the variables

(-1y+7)(2y+9)=0

We multiply parentheses ..

(-2y^2-9y+14y+63)=0

We get rid of parentheses

-2y^2-9y+14y+63=0

We add all the numbers together, and all the variables

-2y^2+5y+63=0

a = -2; b = 5; c = +63;
Δ = b2-4ac
Δ = 52-4·(-2)·63
Δ = 529
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{529}=23$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-23}{2*-2}=\frac{-28}{-4}
=+7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+23}{2*-2}=\frac{18}{-4}
=-4+1/2
$