Bài 1 : tính nhanh a. -28 + 32 – 45 – 32 + 28 + 45 – 8 b. 42 – 56 + 33 – ( 33 – 56 + 42 – 10 ) c. -5 – {- [ – ( -7 ) + ( -10 ) ]} – [ 5 – ( -12 ) –

Question

Bài 1 : tính nhanh
a. -28 + 32 – 45 – 32 + 28 + 45 – 8
b. 42 – 56 + 33 – ( 33 – 56 + 42 – 10 )
c. -5 – {- [ – ( -7 ) + ( -10 ) ]} – [ 5 – ( -12 ) – [ ( -3)- ( -9 ) – 4 -5 ]
d. | x + 2 | = 4

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Nevaeh 17 phút 2021-11-26T06:32:42+00:00 2 Answers 0 views 0

Answers ( )

    0
    2021-11-26T06:33:46+00:00

    `a) -28+32-45-32+28+45-8`

    `= [(-28)+28]+[32+(-32)]+[(-45)+45]+8`

    `= 0+0+0+8`

    `= 8`

    `b) 42-56+33-(33-56+42-10)`

    `= 42-56+33-33+56-42+10`

    `= [42-42]+[(-56)+56]+(33-33)+10`

    `= 0+0+0+10`

    `= 10`

    `c) -5-{-[-(-7)+ ( -10 ) ]} – [ 5 – ( -12 ) – [ ( -3)- ( -9 ) – 4 -5 ]`

    `= -5+[7+(-10)]-[5+12-[(-3)+9-4-5]`

    `= -5+(-3)-[5+12+3+9-4-5]`

    `= -5+(-3)-20`

    `= -28`

    `d) |x+2|= 4`

    TH1: `x+2= 4`                                 TH2: `x+2= -4`

            `x= 4-2`                                           `x= -4-2`

            `x= 2`                                              `x= -6`

    Vậy `x∈{2; -6}`

    0
    2021-11-26T06:34:18+00:00

    Đáp án:

    a)-28 + 32 – 45 – 32 + 28 + 45 – 8

    =(28-28)+(32-32)+(45-45)-8

    =-8

    b. 42 – 56 + 33 – ( 33 – 56 + 42 – 10 )

    =42-56+33-33+56-42+10

    =(42-42)+(56-56)+(33-33)+10

    =10

    c)-5-{-[-(-7)+ ( -10 ) ]} – [ 5 – ( -12 ) – [ ( -3)- ( -9 ) – 4 -5 ]`

    =-5+(-3)-20

    th1=4                                 th2-4

                                                       x

            =2                                              =-6

    Vậy 

     

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