1 2,1,1,?,9 11,11 13是什么答案
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数列问题,裂项求和
9*10/1+10*11/1+11*12/1+12*13/1=9/1-10/1+10/1-11/1+11/1-12/1+12/1-13/1=9/1-13/1=117/4
我想纠正一下汨神的“-1/10*11=-1/10+1/11”应该是-1/10*11=-(11/10)=-1-1/10才对而-1/10+1/11=(10-11)/(10*11)=-1/(10*11)
-1/10×11-1/11×12-1/12×13—……-1/19×20=-(1/10×11+1/11×12+1/12×13—……+1/19×20)=-(1/10-1/11+1/11-1/12+1/12
原式=-(1/10*11+1/11*12+1/12*13……+1/19*20)=-(1/10-1/11+1/11-1/12+1/12-1/13……+1/19-1/20)=-(1/10-1/20)=-1
1/10*11=1/10-1/111/11*12=1/11-1/12……所以原式=(1/10-1/11)+(1/11-1/12)+…+(1/19-1/20)=1/10-1/20=1/20
=-(1/10-1/11+1/11-1/12+1/12-1/13.+1/19-1/20)=-(1/10-1/20)=-1/20
把几分之一设为X,得X+X+X=十一分之十二3X=十一分之十二X=十一分之四
由于1/10*11=1/10-1/111/11*12=1/11-1/121/12*13=1/12-1/13..所以原式==(1/10-1/11)+(1/11-1/12)+(1/12-1/13)+.+(
=1/9-1/10+1/10-1/11+...+1/100-1/101=1/9-1/101=92/909
12×(11/2-12/1)×11=12x11x(11/2-12/1)=12x11x11/2-12x11x12/1=6/1-11/1=66/5
原式=-(1/10-1/11+1/11-1/12+1/12-1/13+……+1/19-1/20)=-(1/10-1/20)=-1/20
-1/10*11=1/11-1/10以此类推得最后为1/20-1/10=-1/20
1/10*11+1/11*12+1/12*13+1/13*14+1/14*15=1/10-1/11+1/11-1/12+1/12-1/13+1/13-1/14+1/14-1/15=1/10-1/15=
(1+1/12)*11-(5/17+11/12)=11+11/12-11/12-5/17=11-5/17=10又12/17再问:你确定是对的吗?再答:对的再问:你能告诉我理由吗?这个答案是怎样得出来的
1/10×11+1/11×12+…+1/19×20=1/10-1/11+1/11-1/12+...+1/19-1/20=1/10-1/20=1/20
外项积等于内项积8(x-12)/11=11×1x-12=121/8x=121/8+12x=217/8
1/4×12/11×(11/12+3/4)=1/4x12/11x11/12+1/4x3/4x12/11=1/4x1+3/16x12/11=1/4+9/44=11/44+9/44=20/44=5/11如
-(1/10-1/11+1/11-1/12-.-1/99+1/99-1/100)=-9/100
您好:|1/11-1/12|+|1/12-1/13|+|1/13-1/14+|1/14-1/15|=1/11-1/12+1/12-1/13+1/13-1/14+1/14-1/15=1/11-1/15=