S=1/51.10+1/10.15+…+1/95.100 CM S<1 Tính A=2/1.4+2/4.7+2/7.10+...+2/97.100 Cần gấp

Question

S=1/51.10+1/10.15+…+1/95.100
CM S<1 Tính A=2/1.4+2/4.7+2/7.10+...+2/97.100 Cần gấp

in progress 0
Maria 4 ngày 2021-09-12T22:58:18+00:00 1 Answers 0 views 0

Answers ( )

    0
    2021-09-12T23:00:05+00:00

    Đáp án:

     

    Giải thích các bước giải:
    S=1/5.10+1/10.15+…+1/95.100
    =1/5(5/5.10+5/10.15+…+5/95.100)
    =1/5(5/5-5/10+5/10-5/15+…+5/95-5/100
    =1/5(5/5-5/100)
    =1/5.19/20
    =19/100
    Vậy S=19/100
    A=2/1.4+2/4.7+…+2/97.100
    =2/3(3/1.4+3/4.7+…+3/97.100)
    =2/3(3-3/4+3/4-3/7+…+3/97-3/100)
    =2/3.(3-3/100)
    =2/3.297/100
    =99/50
    vậy A=99/50
    vote 5*

Leave an answer

Browse

35:5x4+1-9:3 = ? ( )