·3/2-5/6+7/12-9/20+11/30-13/42+…+201/9900-203/10100=?计算结果是多少,如何的计算公式.
·3/2-5/6+7/12-9/20+11/30-13/42+…+201/9900-203/10100=?
计算结果是多少,如何的计算公式.
最后两项错了,
=(1+2)/(1*2)-(2+3)/(2*3)+ +(99+100)/(99*100)-(100+101)/(100*101)
=(1/1+1/2)-(1/2+1/3)+(1/3+1/4)+ +(1/99+1/100)-(1/100+1/101)
=1-1/101
=100/101
100/101
1+1/2-1/2-1/3+1/3+1/4-1/4-1/5……-1/101-1/102=101/102
3/2-5/6+7/12-9/20+11/30-13/42+…+201/9900-203/10100
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)+......+(1/99+1/100)-(1/100+1/101)
=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+......+1/99+1/100-1/100-1/101
=1-1/101
=100/101
(1+2)/(1*2)-(2+3)/(2*3)+(3+4)/(3*4)-.....+(99+100)/(99*100)-(100+101)/(100*101)
=(1/1+1/2)-(1/2+1/3)+(1/3+1/4)-....+(1/99+1/100)-(1/100+1/101)=1/1-1/101=100/101
如果按照规律来算的话,你给的最后两项数字有问题。
分成两个数列,
一列加一列减
分子和分母都是等差
这你们老师应该有教过吧!
是这样的 每一项都是(a+b)/(a*b)
第一项 (1+2)/(1*2),第二项(2+3)/(2*3)..........
(a+b)/(a*b)=1/a+1/b;
因此 原式即为
(1/1+1/2)-(1/2+1/3)+(1/3+1/4)-......-(1/101+1/102)
=1-1/102
你的题目中最后二项应该是:+199/9900-201/10100,
3/2-5/6+7/12-9/20+11/30-13/42+…+199/9900-201/10100
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)...+(1/99+1/100)-(1/100+1/101)
=1-1/101,(中间的部分全都约去了)
=100/101
3/2-5/6+7/12-9/20+11/30-13/42+…+201/9900-203/10100
=3×(1-1/2)-5×(1/2-1/3)+7×(1/3-1/4)-9×(1/4-1/5)+11×(1/5-1/6)-13×(1/6-1/7)+……-203 ×(1/100-1/101)
=3-3/2-5/2+5/3+7/3-7/4-9/4+9/5+11/5-11/6-13/6+13/7+……-203/100+203/101
=3-4+4+4-4……-4+203/101
=102/101
请采纳,谢谢