设x趋向于无穷大,f(x)与1/x是等价无穷小,则3xf(x)的极限是
问题描述:
设x趋向于无穷大,f(x)与1/x是等价无穷小,则3xf(x)的极限是
答
f(x)与1/x是等价无穷小, 即他们可以代替对方
3 x f(x) = 3 x / x = 3
答
即f(x)~1/x
所以极限=lim(x趋于∞)3x*1/x=3