Bài 1 : thực hiện phép tính ( bằng cách hợp lí nếu có thể ) a) 7/13 + 12/13 + 6/-13 b) ( 4/5 + 1/2 ) . ( 6/13 – 2 ) c) -4/10 + 0,9 . ( 1/3 – 1/5 ) :

Question

Bài 1 : thực hiện phép tính ( bằng cách hợp lí nếu có thể )
a) 7/13 + 12/13 + 6/-13
b) ( 4/5 + 1/2 ) . ( 6/13 – 2 )
c) -4/10 + 0,9 . ( 1/3 – 1/5 ) : 10%
Bài 2 : tìm x biết :
a) -13/20 + x = -11/15
b) 0,5x + 2/3x – x = -4

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Reese 4 tuần 2021-08-17T06:36:19+00:00 2 Answers 2 views 0

Answers ( )

    0
    2021-08-17T06:37:24+00:00

    Đáp án:

     

    Giải thích các bước giải:

     1.

    a) 7/13 + 12/13 + 6/-13

    = 7/13 + 12/13 + -6/13

    = -13/13

    = -1

    b) ( 4/5 + 1/2 ) . ( 6/13 – 2 )

    = ( 8/10 + 5/10 ) . ( 6/13 – 26/13 )

    = 13/10 . -20/13

    = -260/130

    =-2

    c) -4/10 + 0,9 . ( 1/3 – 1/5 ) : 10%

    =-4/10 + 9/10 . ( 5/15 – 3/15 ) . 1000/100

    =5/10 . 2/15 . 10

    = 1/2 .2/15 .10

    = 2/30.10

    = 20/30

    = 2/3

    2.

    a) -13/20 + x = -11/15

    x = -11/15 – -13/20

    x = -44/60 + 39/60

    x = -5/60

    x  = -1/12

    b) 0,5x + 2/3x – x = -4

    0,5x + 2/3x – x1 = -4

    x ( 0,5 + 2/3 – 1 ) = -4

    x ( 5/10 + 2/3 – 1 ) = -4

    x ( 15/30 + 20/30 – 30/30 ) = -4

    x 5/30 = -4

    x         = -4 : 5/30

    x         = -4 . 6

    x = -24

    0
    2021-08-17T06:37:40+00:00

    Đáp án:

     

    Giải thích các bước giải:

    a) $\cfrac{7}{13}+\cfrac{12}{13}+\cfrac{6}{-13}\\=\cfrac{7}{13}+\cfrac{12}{13}+\cfrac{-6}{13}\\=\cfrac{7+12+6}{13}\\=\cfrac{25}{13}$

    b) $(\cfrac{4}{5}+\cfrac{1}{2})(\cfrac{6}{13}-2)\\=+\cfrac{4\times 2+5\times 1}{5\times 2}(\cfrac{6}{13}-2)\\=\cfrac{13}{10}(\cfrac{6+13\times 2}{13})\\=\cfrac{6+13\times 2}{10}\\=\cfrac{3+13}{5}\\=\cfrac{16}{5}$

    c) $-\cfrac{4}{10}+0,9(\cfrac{1}{3}-\cfrac{1}{5})\div 10\%\\=-\cfrac{2}{5}+0,9(\cfrac{1}{3}-\cfrac{1}{5})\times 10\\=\cfrac{2}{5}+9\times \cfrac{2}{15}\\=\cfrac{2}{5}+\cfrac{18}{15}\\=\cfrac{2\times 3+18}{15}\\=\cfrac{8}{5}$

    Bài 2:

    a) $-\cfrac{13}{20}+x=-\cfrac{11}{15}\\\Leftrightarrow x=\cfrac{-11}{15}+\cfrac{13}{20}\\\Leftrightarrow x=\cfrac{13}{20}+(-\cfrac{11}{15})\\\Leftrightarrow x=-\cfrac{1}{12}$

    b) $0,5x+\cfrac{2}{3}x-x=-4\\\Leftrightarrow x(0,5+\cfrac{2}{3}-1)=-4\\\Leftrightarrow x(\cfrac{1}{2}+\cfrac{2}{3}-1)=-4\\\Leftrightarrow x(\cfrac{2}{3}-\cfrac{1}{2})=-4\\\Leftrightarrow \cfrac{1}{6}x=-4\\\Leftrightarrow x=-4\times 6\\\Leftrightarrow x=-24$

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