题目中f(x)f(x)=4,g(x)g(x)=8
应该是f(x)f(y)=4,g(x)g(y)=8
f(x)f(y)
=(e^x—e^-x)(e^y—e^-y)
=e^(x+y)—e^(x-y)-[e^-(x-y)]+e^-(x+y)
=g(x+y)-g(x-y)
=4
g(x)g(y)
=e^(x+y)+e^(x-y)+[e^-(x-y)]+e^-(x+y)
=g(x+y)+g(x-y)=8
g(x+y)-g(x-y)=4 .(1)
g(x+y)+g(x-y)=8 ...(2)
===>
g(x+y)=6
g(x-y)=2
======> g(x+y)/g(x-y) =3