已知A=x-y/x+y,B=xy/x+y,当x y的值都扩大为原来的3倍时 A B得值有何变化

问题描述:

已知A=x-y/x+y,B=xy/x+y,当x y的值都扩大为原来的3倍时 A B得值有何变化

因为A=x-y/x+y, B=xy/x+y
则当x y的值都扩大为原来的3倍时 ,
(3x﹣3y)/(3x+3y) = 3(x﹣y)/3(x+y) = (x﹣y)/(x+y) = A ,
3x*3y/(3x+3y) = 9xy/3(x+y) = 3xy/(x+y) = 3B
所以当x y的值都扩大为原来的3倍时,A值不变,B值扩大3倍

A不变,B变为原来的3倍