Given
Mx(t) = exp(t^2 + 2t)
My(t) = exp(3t^2 + t)
Find the mgf of X + 2Y.
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Can anybody explain how
My(2t) = exp(12t^2 + 2t) ???? I figured this going backwards from the answer...so it may be wrong...
THANKS
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The answer is exp(13t^2 + 4t)