Consider the function \(J ( a ) = \sum _ { n = 0 } ^ { \infty } n e ^ { - a n }\) defined for positive a .
Write an explicit expression for J(a).
Expand J(a) around the point a = 0 up to \(O ( a ^ { 0 } )\)
P-TRIV-RA55
Consider the function \(J ( a ) = \sum _ { n = 0 } ^ { \infty } n e ^ { - a n }\) defined for positive a .
Write an explicit expression for J(a).
Expand J(a) around the point a = 0 up to \(O ( a ^ { 0 } )\)