0.275≤（0.7a+0.02b）/（a+b）≤0.28
问题描述：
0.275≤（0.7a+0.02b）/（a+b）≤0.28
1.4≤a+b≤1.5
求a和b的取值范围
12.75≤ 34a/（a+b）≤13
倒过来
1/12.75≤ 1/34+b/34a ≤1/13
错了吧1/12.75>1/13的吧
答
0.275≤（0.7a+0.02b）/（a+b）≤0.28两遍除以0.0213.75≤ （34a+a+b）/（a+b）≤14两边减112.75≤ 34a/（a+b）≤13倒过来1/12.75≤ 1/34+b/34a ≤1/13两边减1/34再乘以3485/51≤ b/a ≤ 21/13两边乘以a85a/51≤ b ...