Integrate 3e^x
To integrate 3e^x, also written as ∫3ex dx, we realise that "3" is a constant multiplier that could be taken outside of the integral.
With the numeral constant brought outside, we see that the integral is still the same but easier to perform.
We know that ∫ex dx = ex + C, which is the easiest one in calculus to perform.
Finally, we multiply with the constant "3", to give the answer.