（1）F(2)G(3)+F(2)G(3) =(1/4)[(a^2+a^(-2))(a^3-a^(-3))]+(1/4)[(a^3+a^(-3))(a^2-a^(-2))] =(1/4)[a^5+a-a^(-1)-a^(-5)]+(1/4)[a^5-a+a^(-1)-a^(-5)] =(1/2)[a^5-a^(-5)] =G(5). （2）G(x+y)=F(x)G(y)+G(y)F(x) [证明从略]
