f(2)+f(1)-4=30-4=

Solution for f(2)+f(1)-4=30-4= equation:

f(2)+f(1)-4=30-4=

We move all terms to the left:

f(2)+f(1)-4-(30-4)=0

We add all the numbers together, and all the variables

f2+f1-4-26=0

We add all the numbers together, and all the variables

f^2+f-30=0

a = 1; b = 1; c = -30;
Δ = b2-4ac
Δ = 12-4·1·(-30)
Δ = 121
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{121}=11$
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-11}{2*1}=\frac{-12}{2}
=-6
$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+11}{2*1}=\frac{10}{2}
=5
$