# Homework Help: Find energy of signal

1. Aug 18, 2010

### drkidd22

1. The problem statement, all variables and given/known data

x(t) = e(-2t) * u(t)

Ex = x2(t) dt

Attached is the work I have done. Got stuck towards the end.

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2. Aug 19, 2010

### xcvxcvvc

$$(e^{-2x})^2 = e^{-2x}e^{-2x}=e^{-2x-2x}=e^{-4x}$$
or you can use the power property associated with exponents and instantly say
$$(e^{-2x})^2=e^{2(-2x)}=e^{-4x}$$
I'm assuming the exponential being squared is what messed you up, and I'm assuming you can take it from here.