# Thread: la place transform of t^2e^(-2t) from definition

1. ## la place transform of t^2e^(-2t) from definition

if i try to write out what i did on this it will be very messy, but my final answer was:

1/(s+2) - 1/((s+2)^2) - 1/((s+2)^3) , s =/= -2

is this right?

2. You should eliminate the mess and somehow lose the first two pieces.

Do t^2 and e^(-2t) separately and get an idea of where you are aiming.

3. If you are using the definition, you should know that

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It's not pretty, but here you go...

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Of course, it's much, much, much easier to use the fact that , because then...

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4. thanks for that.. one question..
why do you differenciate the first term only in the 6th line, and why is that acceptable?

i.e when lim {ε^2/e^((s+2)ε)} goes to lim {2ε/[(2+s)e^(2+s)ε]}

5. I didn't, I used L'Hospital's Rule.

6. ahhhh yes i see... thanks heaps