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

问题描述:

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

因为a-b除以a+b=7
所以a-b除以3(a+b)=7/3,a+b除以a-b=1/7
所以2(a+b)除以a-b=2/7
所以原式=2/7-7/3=-43/21

答案是-43/21

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...