首页 > 留学知识库

问题: x是有理数,求|x-100/221|+|x+95/221|的最小值。

要准确!!!谢谢!!

解答:

x是有理数,求y = |x - 100/221| + |x + 95/221|的最小值。

1、当x≥100/221时
y = |x - 100/221| + |x + 95/221|
= x - 100/221 + x + 95/221
= 2x - 5/221
当x = 100/221时取得最小值
ymin = 2×100/221 - 5/221 = 15/17

2、当-95/221≤x<100/221时
y = |x - 100/221| + |x + 95/221|
= -x + 100/221 + x + 95/221
= 195/221
= 15/17

3、x<-95/221时
y = |x - 100/221| + |x + 95/221|
= 100/221 - x - x - 95/221
= -2x + 5/221
当x = -95/221时取得最小值
ymin = 2×95/221 + 5/221 = 285/17

所以y = |x - 100/221| + |x + 95/221|的最小值为
ymin = 15/17