0.275≤(0.7a+0.02b)/(a+b)≤0.28
1个回答

0.275≤(0.7a+0.02b)/(a+b)≤0.28

两遍除以0.02

13.75≤ (34a+a+b)/(a+b)≤14

两边减1

12.75≤ 34a/(a+b)≤13

倒过来

1/12.75≤ 1/34+b/34a ≤1/13

两边减1/34再乘以34

85/51≤ b/a ≤ 21/13

两边乘以a

85a/51≤ b ≤ 21a/13

当b=21a/13时

1.4≤34a/13≤1.5

此时91/170≤a≤39/68,147/170≤b≤63/68

当b=85a/51时

1.4≤136a/51≤1.5

此时357/850≤a≤153/272,7/10≤b≤255/272

各取极限值

357/850≤a≤39/68,7/10≤b≤63/68

额.差不多就这意思.思路.主要是思路.