[離散] generating function的證明

[mqazz1 (無法顯示)]

prove the following equation with generating function:

[C(n, 0)]^2 + [C(n,1)]^2 + ... + [C(n,n)]^2  =  C(2n, n)

請問要如何證明這個式子呢?

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→ Sfly        :(1+x)^n(1+x)^2=(1+x)^2n