-215f+70=-15f^2

Solution for -215f+70=-15f^2 equation:

-215f+70=-15f^2

We move all terms to the left:

-215f+70-(-15f^2)=0

We get rid of parentheses

15f^2-215f+70=0

a = 15; b = -215; c = +70;
Δ = b2-4ac
Δ = -2152-4·15·70
Δ = 42025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{42025}=205$
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-215)-205}{2*15}=\frac{10}{30}
=1/3
$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-215)+205}{2*15}=\frac{420}{30}
=14
$