7n(5-7n)=0

Solution for 7n(5-7n)=0 equation:

7n(5-7n)=0

We add all the numbers together, and all the variables

7n(-7n+5)=0

We multiply parentheses

-49n^2+35n=0

a = -49; b = 35; c = 0;
Δ = b2-4ac
Δ = 352-4·(-49)·0
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(35)-35}{2*-49}=\frac{-70}{-98}
=5/7
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(35)+35}{2*-49}=\frac{0}{-98}
=0
$