(-4f+1)(5f-8)=0

Solution for (-4f+1)(5f-8)=0 equation:

(-4f+1)(5f-8)=0

We multiply parentheses ..

(-20f^2+32f+5f-8)=0

We get rid of parentheses

-20f^2+32f+5f-8=0

We add all the numbers together, and all the variables

-20f^2+37f-8=0

a = -20; b = 37; c = -8;
Δ = b2-4ac
Δ = 372-4·(-20)·(-8)
Δ = 729
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{729}=27$
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(37)-27}{2*-20}=\frac{-64}{-40}
=1+3/5
$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(37)+27}{2*-20}=\frac{-10}{-40}
=1/4
$