Question

求大神给个详细点的解释

Answer 1

y->+∞

1/y ->0+
ln(1+1/y) ~ 1/y
1/y=3/x^2
ln(1+3/x^2) ~ 3/x^2

追问

追答

y->∞
ln(1+1/y) = 1/y +o(1/y)
代入
1/y = 3/x^2
ln(1+3/x^2) = 3/x^2 +o(1/x^2)