呢條數點計？？？？？
回答 (1)
2020-10-08 9:49 pm
(a)
k = f(0) = 3
(b)
(i) f(x) ≦ 3 if and only if 0 ≦ x ≦ 2 or x ≧ 4.
(ii) x^3 - 6x^2 + 8x = -2(f(x) - k) = 6 - 2f(x)
∴ x^3 - 6x^2 + 8x ≦ 0
if and only if 6 - 2f(x) ≦ 0
if and only if f(x) ≧ 3
if and only if x ≦ 0 or 2 ≦ x ≦ 4.
k = f(0) = 3
(b)
(i) f(x) ≦ 3 if and only if 0 ≦ x ≦ 2 or x ≧ 4.
(ii) x^3 - 6x^2 + 8x = -2(f(x) - k) = 6 - 2f(x)
∴ x^3 - 6x^2 + 8x ≦ 0
if and only if 6 - 2f(x) ≦ 0
if and only if f(x) ≧ 3
if and only if x ≦ 0 or 2 ≦ x ≦ 4.
收錄日期: 2021-05-04 02:32:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20201008130409AAyKsKM