f(7f+3)=0

Solution for f(7f+3)=0 equation:

f(7f+3)=0

We multiply parentheses

7f^2+3f=0

a = 7; b = 3; c = 0;
Δ = b2-4ac
Δ = 32-4·7·0
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-3}{2*7}=\frac{-6}{14}
=-3/7
$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+3}{2*7}=\frac{0}{14}
=0
$