(3又7/1)X(3又7/1-7又3/1)X22/7X22/21

问题描述:

(3又7/1)X(3又7/1-7又3/1)X22/7X22/21

(3又7/1)X(3又7/1-7又3/1)X22/7X22/21
=7/22X22/7X22/21X(3又7/1-7又3/1)
=22/21X(3又7/1-7又3/1)
=22/21X7/22-22/21X3/22
=3-7
=-4