use substitution in the power series e^x=1+x+(x^2/2!)+(x^3)/3!)+... to find a power series expansion for f(x)=e^(-2x)

Question

use substitution in the power series e^x=1+x+(x^2/2!)+(x^3)/3!)+... to find a power series expansion for f(x)=e^(-2x)

Answer 1

Just replace x with -2x in the power series expansion for e^x.