如果是选择填空题,直接选4个数代入比如a=2,b=1,c=-2,d=-1可知b/(a-c)＜a/(b-d)如果是要过程的题目用相减法b/(a-c)-a/(b-d)=[b(b-d)-a(a-c)]/(a-c)(b-d)分母＞0分子=b^2-a^2+(ac-bd)b^2-a^2＜0ac＜0,bd＜0,且ac/bd=(a...