(1/3+1/5+1/7+1/9)*(1/5+1/7+1/9+1/11)-(1/3+1/11+1/5+1/7+1/9)*1/5+1/7+1/9)简便运算可以将1/5+1/7+1/9设为a
问题描述：
(1/3+1/5+1/7+1/9)*(1/5+1/7+1/9+1/11)-(1/3+1/11+1/5+1/7+1/9)*1/5+1/7+1/9)简便运算
可以将1/5+1/7+1/9设为a
答
原式=（1/3+a）*（a+1/11)-(1/3+1/11+a)*a
=1/3a方+1/3a+1/33
然后再把1/5+1/7+1/9=a代入