(7-y)(2y+5)=0

Solution for (7-y)(2y+5)=0 equation:

(7-y)(2y+5)=0

We add all the numbers together, and all the variables

(-1y+7)(2y+5)=0

We multiply parentheses ..

(-2y^2-5y+14y+35)=0

We get rid of parentheses

-2y^2-5y+14y+35=0

We add all the numbers together, and all the variables

-2y^2+9y+35=0

a = -2; b = 9; c = +35;
Δ = b2-4ac
Δ = 92-4·(-2)·35
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-19}{2*-2}=\frac{-28}{-4}
=+7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+19}{2*-2}=\frac{10}{-4}
=-2+1/2
$