已知a-b除以a+b=7,求2(a+b)除以a-b 减 a-b除以3（a+b）的值

Question

已知a-b除以a+b=7,求2(a+b)除以a-b 减 a-b除以3（a+b）的值

Answer 1

因为：(a - b)/(a + b) = 7
所以,(a +b）／(a - b) = 1/7
因此,2(a + b)/(a - b) - ( a-b)/ 3(a + b)
= 2 ×（a + b)/( a - b) - (1/3) × (a - b)/(a + b)
= 2 × 1/7 - 1/3 × 7
= 2/7 - 7/3
= 6/21 - 49/21
= - 43/21