given that f(x)=13x^2+156, find x

Simplifying
f(x) = 13x2 + 156

Multiply f * x
fx = 13x2 + 156

Reorder the terms:
fx = 156 + 13x2

Solving
fx = 156 + 13x2

Solving for variable 'f'.

Move all terms containing f to the left, all other terms to the right.

Divide each side by 'x'.
f = 156x-1 + 13x