-7y(3-5y)=0

Solution for -7y(3-5y)=0 equation:

-7y(3-5y)=0

We add all the numbers together, and all the variables

-7y(-5y+3)=0

We multiply parentheses

35y^2-21y=0

a = 35; b = -21; c = 0;
Δ = b2-4ac
Δ = -212-4·35·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-21}{2*35}=\frac{0}{70}
=0
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+21}{2*35}=\frac{42}{70}
=3/5
$