一道关于函数连续性的题目,
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/11/08 03:45:42
一道关于函数连续性的题目,
请写出步骤和思路.
请写出步骤和思路.
由于
lim(x→0)[f(x)/x] = 0,
知 f(0) = 0.
做替换u = xt,则t = u/x,dt = du/x,于是,
g(x) = ∫[0,1]f(xt)dt = (1/x)∫[0,x]f(u)du,
应有 g(0) = 0.
于是,当x ≠ 0时,
g'(x) =(1/x^2)[xf(x)-∫[0,x]f(u)du],
当x = 0时,
g'(0)= lim(x→0) [g(x) - g(0)]/x
= lim(x→0) [(1/x)∫[0,x]f(u)du - 0]/x
= lim(x→0) [∫[0,x]f(u)du]/x^2 (0/0)
= lim(x→0)f(x)/2x
= A/2.
于是
lim(x→0) g'(x) = lim(x→0) [xf(x)-∫[0,x]f(u)du]/x^2
= lim(x→0) [f(x)/x] - lim(x→0) [∫[0,x]f(u)du]/x^2}
= A - A/2 = A/2 =g'(0),
即g'(x)在x = 0连续.
lim(x→0)[f(x)/x] = 0,
知 f(0) = 0.
做替换u = xt,则t = u/x,dt = du/x,于是,
g(x) = ∫[0,1]f(xt)dt = (1/x)∫[0,x]f(u)du,
应有 g(0) = 0.
于是,当x ≠ 0时,
g'(x) =(1/x^2)[xf(x)-∫[0,x]f(u)du],
当x = 0时,
g'(0)= lim(x→0) [g(x) - g(0)]/x
= lim(x→0) [(1/x)∫[0,x]f(u)du - 0]/x
= lim(x→0) [∫[0,x]f(u)du]/x^2 (0/0)
= lim(x→0)f(x)/2x
= A/2.
于是
lim(x→0) g'(x) = lim(x→0) [xf(x)-∫[0,x]f(u)du]/x^2
= lim(x→0) [f(x)/x] - lim(x→0) [∫[0,x]f(u)du]/x^2}
= A - A/2 = A/2 =g'(0),
即g'(x)在x = 0连续.