Question

3乘5分之1加5乘7分之1加7乘9分之1加9乘11分之1简便算式

Answer 1

原式=1/2(1/3-1/5)+1/2(1/5-1/7)+1/2(1/7-1/9)+1/2(1/9-1/11)
=1/2(1/3-1/11)
=1/2*(11-3)/33
=4/33