Evaluate: int_0^(oo) ((1-e^(-px))(1-e^(-qx))(1-e^(-rx)))/(e^x) dx, p>0, q>0, r>0

fabler107

fabler107

Answered question

2022-11-08

Evaluate:
0 ( 1 e p x ) ( 1 e q x ) ( 1 e r x ) e x d x ,       p > 0 ,   q > 0 ,   r > 0
I try it with laplace transfrom, but I cant find a result

Answer & Explanation

Aiden Villa

Aiden Villa

Beginner2022-11-09Added 10 answers

Use the substitution e x = t
This transforms the integral into
0 1 ( 1 t p ) ( 1 t q ) ( 1 t r ) d t
= 0 1 ( t p + q + r + t p + q + t p + r t p + t q + r t q t r + 1 ) d t
= 1 + 1 p + q + 1 + 1 p + r + 1 + 1 q + r + 1 1 p + q + r + 1 1 p + 1 1 q + 1 1 r + 1
which seems to check out numerically.

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