然后1/15*17*5=17/3,1/51*17*5=5/3,两者相减=12/3=4
(1/15-1/51)*17*5
=1/15*17*5-1/51*17*5
=1/3*17-1/3*5
=17/3-5/3
=4
不懂可追问,有帮助请采纳,谢谢!
后面就约分 相乘啊 然后做减法就OK了
即17/3-5/3=4
(1/15-1/51)*17*5
=(1/15X5)X17-(1/51X17)X5
=[1/(3X5) X5]X17-[1/(3X17) X17]X5
=1/3X17-1/3X5
=1/3X(17-5)
=1/3X12
=1/3X3X4
=4
x=自己算吧