21×1.721✘1.7
(3/1+7/2)✘21??
(3/1+7/2)21
这里可以约分🦬🐡-|🤭,首先合成=>21/(12*7)=>(3*7)/(12*7)=>3/12=>1/4
计算(+3又1/7)✘(-7又1/3)✘7/22✘21/22??(3/1+7/2)21
这里可以约分🦬🐡-|🤭,首先合成=>21/(12*7)=>(3*7)/(12*7)=>3/12=>1/4
(+3又1/7)✘(-7又1/3)✘7/22✘21/22 =-22/7×22/7×7/22×21/22 =-21/7 =-3