Given df/dx=2x+3 and the graph goes through (1,1), what is the function f?

First step: integrate int df/dx = x^2+3x+c (never forget the constant!) 

Second step: substitute the point in order to get c 

1 = (1)^2+3*1+c -> c = 1-1-3=-3

Thus, f = x^2+3x-3