1/9X10+1/10X11+1/11X12+1/12X13+…+1/17X18=
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/28 06:30:25
![1/9X10+1/10X11+1/11X12+1/12X13+…+1/17X18=](/uploads/image/z/15160000-40-0.jpg?t=1%2F9X10%2B1%2F10X11%2B1%2F11X12%2B1%2F12X13%2B%E2%80%A6%2B1%2F17X18%3D)
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1/9X10+1/10X11+1/11X12+1/12X13+…+1/17X18=
1/9X10+1/10X11+1/11X12+1/12X13+…+1/17X18=
1/9X10+1/10X11+1/11X12+1/12X13+…+1/17X18=
1/9X10+1/10X11+1/11X12+1/12X13+…+1/17X18
=1/9-1/10+1/10-1/11+1/11-1/12+1/12-1/13+...+1/17-1/18
=1/9-1/18
=1/18
1/(9*10)+1/(10*11)+1/(11*12)+1/(12*13)+…+1/(17*18)
=(1/9)-(1/10)+(1/10)-(1/11)+(1/11)-(1/12)+...+(1/17)-(1/18)
=(1/9)-(1/18)
=1/18.