f(-4)=-5,f(2)=-3

Solution for f(-4)=-5,f(2)=-3 equation:

f(-4)=-5.f(2)=-3

We move all terms to the left:

f(-4)-(-5.f(2))=0

We add all the numbers together, and all the variables

-(-5f^2)+f(-4)=0

We multiply parentheses

-(-5f^2)-4f=0

We get rid of parentheses

5f^2-4f=0

a = 5; b = -4; c = 0;
Δ = b2-4ac
Δ = -42-4·5·0
Δ = 16
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16}=4$
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-4}{2*5}=\frac{0}{10}
=0
$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+4}{2*5}=\frac{8}{10}
=4/5
$