In the expansion of(x-(a/x))^5 *(x+(a/x))^5 ...

题目

In the expansion of(x-(a/x))^5 *(x+(a/x))^5 ...
In the expansion of (x-(a/x))^5 *(x+(a/x))^5,where a is a non-zero constant,the
coefficient of the term in x^(-2) is ‘–9’ times the coefficient in x^2 .Find the value of
the constant a.

答案