y = e^(-3x) - e^(2x) = e^(-3x) (1 - e^(5x)) = 0
1 - e^(5x) = 0
1 = e^(5x)
ln 1 = ln e^(5x) = 5x
ln 1 = 0
∴ x = 0/5 = 0
Moderator edit: Quote of OP has been added. This post answers the original question posted. However, it should be noted that in post #3 the original poster gave a new question.