f(2)=3(4)+1

Solution for f(2)=3(4)+1 equation:

f(2)=3(4)+1

We move all terms to the left:

f(2)-(3(4)+1)=0

We add all the numbers together, and all the variables

f2-35=0

We add all the numbers together, and all the variables

f^2-35=0

a = 1; b = 0; c = -35;
Δ = b2-4ac
Δ = 02-4·1·(-35)
Δ = 140
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{140}=\sqrt{4*35}=\sqrt{4}*\sqrt{35}=2\sqrt{35}$
$f_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{35}}{2*1}=\frac{0-2\sqrt{35}}{2}
=-\frac{2\sqrt{35}}{2}
=-\sqrt{35}
$
$f_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{35}}{2*1}=\frac{0+2\sqrt{35}}{2}
=\frac{2\sqrt{35}}{2}
=\sqrt{35}
$