若x,m,n,y与p,y,q,x是两个等差数列则m-n/p-q
问题描述：
若x,m,n,y与p,y,q,x是两个等差数列则m-n/p-q
答
x,m,n,y是等差数列,公差d1
则
y-x=3d1
m-n=d1
p,y,q,x是等差数列,公差d2
则
x-y=2d2
p-q=-2d2
m-n/p-q
=d1/(-2d2)
=[(y-x)/3]/[-(x-y)]
=-1/3