[15分之1加35分之一加63分之一]除以15分之7
来源:学生作业帮助网 编辑:作业帮 时间:2024/05/27 20:27:44
1/6+1/12+1/20+1/30+1/42+1/56+1/72=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9=1/2-1/9=7/
1/5+1/15+1/35+1/36=1/5×(1+1/3+1/7)+1/36=1/5×(31/21)+1/36=1/(5×21×36)×(31×36+5×21)=407/1260
1加2又6分之1加3又12分之一加4又20分之一加5有30分之一加6又42分之一加7又56分之一加8又72分之一=1+2+3+4+5+6+7+8+1/6+1/12+1/20+1/30+1/42+1/5
做几分之一加几分之一时有个快捷方法 .
原式=1/(1x3)+1/(3x5)+1/(5x7)+1/(7x9)+1/(9x11)+1/(11x13)+1/(13x15)+1/(15x17)=(1-2/3)+(2/3-3/5)+(3/5-4/7
1又3分之一加3又15分之一加5又35分之一加7又63分之一加9又99分之一=(1+3+5+7+9)+(1/3+1/15+1/35+1/63+1/99)=25+1/2(1-1/3+1/3-1/5+1/
1/15+1/35+1/63+1/99+1/143={[(1/3)-(1/5)]/2}+{[(1/5)-(1/7)]/2}+{[(1/7)-(1/9)]/2}+{[(1/9)-(1/11)]/2}+{
1/6+1/12+1/20+1/42+1/56+1/72+1/90=(2+1)/12+(21+10+7.5)/420+(10+8)/720=1/4+11/120+1/40=(30+11+3)/120=
99/100
3分之1加15分之1加35分之1加63分之1加99分之1加143分之1=1/3+1/2(1/3-1/5)+1/2(1/5-1/7)+1/2(1/7-1/9)+1/2(1/9-1/11)+1/2(1/1
1/3+1/15+1/35+1/63+1/99+1/143=1/3+1/(3*5)+1/(5*7)+1/(7*9)+1/(9*11)+1/(11*13)=1/3+(1/3-1/5+1/5-1/7+1/
1/3+1/15+1/35+1/63+1/99+1/1431/3=1/(1*3)=(1-1/3)/2;同理:1/15=1/(3*5)=(1/3-1/5)/2然后就得到1/3+1/15+1/35+1/6
1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45=(1/3+1/6)+(1/10+1/15)+(1/21+1/28)+(1/36+1/45)=(2+1)/6+(3+2)/30
R1和R2上的U相等,即R1*I1=R2*I2,而总的I=U/R=I1+I2=U/R1+U/R2,消掉U,即得1/R=1/R1+1/R2.
1/3+1/15+1/35+1/63=1/(1×3)+1/(3×5)+1/(5×7)+1/(7×)=1/2×[2/(1×3)+2/(3×5)+2/(5×7)+2/(7×)]=1/2×(1-1/3+1/
原式=(1/2)(1/2-1/4+1/3-1/5+1/4-1/6+...+1/11-1/13)=(1/2)(1/2+1/3-1/12-1/13)=(1/2)(5/12+10/39)=(1/2)(65/
1/15=1/2(1/3-1/5)1/35=1/2(1/5-1/7)1/63=1/2(1/7-1/9).所以原式=60*1/2(1/3-1/5+1/5-1/7+.+1/13-1/15)=30*(1/3
1/2+1/6+1/12+……+1/9900=1-1/2+1/2-1/3+1/3-1/4+……+1/99-1/100=1-1/100=99/100
1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10=1-1/10=9/10这是1/2+1/6+1/12+1/20+