(3x-1)/(3x+1)
把 3x-1 变成 3x+1 -2
=(3x+1-1)/(3x+1)
分开
=1-2/(3x+1)
令
1/y =2/(3x+1)
3x+1 =2y
3x-1 =2y -2
lim(x->+无穷) [(3x-1)/(3x+1)]^(3x-1)
=lim(x->+无穷) [1 - 2/(3x+1)]^(3x-1)
利用 1/y =2/(3x+1)
=lim(y->+无穷) [1 - 1/y]^(2y-2)
=lim(y->+无穷) [1 - 1/y]^(2y)
=e^(-2)
所以得出结果
lim(x->+无穷) [(3x-1)/(3x+1)]^(3x-1) = e^(-2)