A=5/9+2/15-6/9 B=2/7-3/8+4/7+1/7-5/8+5/15 C=3/5+1/15+1/57+1/3-2/9-3/4-1/36 D=1/1×2+1/2×3+1/3×4+…+1/99×100 E=1-3/1×3-3/3×5-3/5×7-…-19

Question

A=5/9+2/15-6/9
B=2/7-3/8+4/7+1/7-5/8+5/15
C=3/5+1/15+1/57+1/3-2/9-3/4-1/36
D=1/1×2+1/2×3+1/3×4+…+1/99×100
E=1-3/1×3-3/3×5-3/5×7-…-19

in progress 0
Lệ Thu 5 years 2021-05-19T10:27:55+00:00 2 Answers 25 views 0

Answers ( )

  1. Sigrid
    0
    2021-05-19T10:29:31+00:00
    Reply

    A=5/9+2/15-6/9=(5/9-6/9)+2/15=-1/9+2/15=-5/45+6/45=1/45

    B=2/7-3/8+4/7+1/7-5/8+5/15=(2/7+1/7+4/7)-(3/8+5/8)+5/15=1-1+1/3=1/3

    C=3/5+1/15+1/57+1/3-2/9-3/4-1/36=(3/5+1/15+1/3)-(2/9+3/4+1/36)+1/57

      =(9/15+1/15+5/15)-(8/36+27/36+1/36)+1/57=1-1+1/57=1/57

    D=1/1×2+1/2×3+1/3×4+…+1/99×100=1-1/2+1/2-1/3+1/3-1/4+…+1/99-1/100

      =1-1/100=99/100

    E=1-3/1×3-3/3×5-3/5×7-…-19=1-(3/1×3+3/3×5+3/5×7+…+19)=1-3(1/1×3+1/3×5+1/5×7+…+19)

       =1-3(1-1/3+1/3-1/5+1/5-1/7+…+19)=1-3(1+19)=1-3.20=1-60=-59

  2. thongdat2
    0
    2021-05-19T10:29:40+00:00
    Reply

    Câu cuối mik ko bít làm nha

    a-5-9-2-15-6-9-b-2-7-3-8-4-7-1-7-5-8-5-15-c-3-5-1-15-1-57-1-3-2-9-3-4-1-36-d-1-12-1-23-1-34-1-99

Leave an answer

Browse

Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )