两道关于高一指数函数的计算题

1）
x^1/2+x^-1/2=3
（x^1/2+x^-1/2）^2=9
x+1/x+2=9
x+1/x=7
(x+1/x)^2=49
x^2+x^-2+2=49
x^2+x^-2=47
x^3/2+x^-3/2
=(x^1/2+x^-1/2)(x-1+1/x)
=3(7-1)=18
(x^2+x^-2-2)/(x^3/2+x^-3/2-3)
=(47-2)/(18-3)
=45/15
=3
2)8^a+8^-a=2^3a+2^-3a
=(2^a+2^-a)(2^2a+2^-2a-1)
=3((2^a+2^-a)^2-2-1)
=3(3^2-3)
=3*6
=18