differentiation

Becaus e^x = 1 + x + (x^2)/2 + (x^3)/3 + ..... + (x^n)/n

then derivative with x
= 0 + 1 + (2x)/2 + (3x^2)/3 + ....
= e^x

therefore, if y=e^x, then dy/dx = e^x

Now, for y = e^3x,
Let u = 3x, du/dx = 3

y = e^u

dy/du = e^u

then
dy/dx = dy/du x du/dx
dy/dx = e^u x 3
dy/dx = (e^3x)3
dy/dx = 3e^3x

what is e??
is it a constant??
If yes,
d/dx(e^3x)
=3xe^(3x-1)