Finding the equation of a tangent line. Find the equation of the tangent to:
A) f(x)= e^3x at (0,1)
B) f(x)= e^-2x at (0,1)
C) f(x)= e^1-x at (1,1)
D) f(x)= e^-2x+x^2 at (2,1)
E) y= xe^x-e^x at (1,0)