第2个回答 2020-11-01
lim(x->0) [ sin(x^3)/x^4 -f(x)/x^3] =5
lim(x->0) [ sin(x^3)-xf(x)]/x^4 =5
x->0
sin(x^3) = x^3 +o(x^4)
sin(x^3) -xf(x) = x^3 -xf(x) +o(x^4)
sin(x^3) -xf(x) = x^3 -xf(x) +o(x^4) = 5x^4 +o(x^4)
=>
f(x) = x^2 - 5x^3 +o(x^3)
f(x) 是x^3 的低价无穷小
ans :B本回答被提问者采纳