The opposite operation to taking a derivative is an integral. Integrate to find original function.
f(x) = x^2 + x + C
C is constant because we didn't have bounds on the integral. it lets you choose the input value let's say is just (1,0)
0 = 1 + 1 + C
- 2 = C
function at input value (1,0)
f(x) = x^2 + x - 2
now if you check by taking derivative is :
f' = 2x + 1
