Question

已知a/b=5/13,求a－b／a＋b的值

Answer 1

已知a/b=5/13两边同时乘以b得 a=5/13b将 a=5/13b 代入a－b／a＋b得a－b／a＋b=(5/13b-b)/(5/13b+b) {这一步就是把a换成5/13b}=(-8/13b)/(18/13b) {(5/13b-b)=-8/13b,(5/13b+b) =18/13b}=-8/18 {分母分子同时乘以13b}...