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

Solution for (3+y)(4y-7y)=0 equation:

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

We add all the numbers together, and all the variables

(y+3)(-3y)=0

We multiply parentheses ..

(-3y^2-9y)=0

We get rid of parentheses

-3y^2-9y=0

a = -3; b = -9; c = 0;
Δ = b2-4ac
Δ = -92-4·(-3)·0
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-9}{2*-3}=\frac{0}{-6}
=0
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+9}{2*-3}=\frac{18}{-6}
=-3
$