Tìm x,bết a, |x – 2,5|- 3/4 = 0 b, 1/2 – |5/2 – 2x|= 1/3 c, |0,5x – 2|-|x + 2/3|=0 d, 2x – |x + 1|= 1/2

Question

Tìm x,bết
a, |x – 2,5|- 3/4 = 0
b, 1/2 – |5/2 – 2x|= 1/3
c, |0,5x – 2|-|x + 2/3|=0
d, 2x – |x + 1|= 1/2

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Samantha 2 tuần 2021-07-12T12:43:13+00:00 1 Answers 0 views 0

Answers ( )

    0
    2021-07-12T12:45:06+00:00

    Đáp án:

    `a)`

    ` |x-2,5| – 3/4 = 0`

    ` |x-2,5| = 3/4`

    Trường hợp `1`

    ` x -2,5 = 3/4`

    ` x – 2,5 = 0,25`

    ` x =0,25 +2,5 = 2,75`

    Trường hợp `2`

    ` x -2,5 = -0,25`

    ` x =-0,25 +2,5`

    ` x = 2,25`

    `b)`

    ` 1/2 – |5/2 -2x| = 1/3`

    ` |5/2 – 2x| = 1/2 – 1/3 = 1/6`

    `TH1` 

    ` 5/2 -2x = 1/6`

    ` 2x = 7/3`

    ` x = 7/6`

    `TH2`

    ` 5/2 -2x = -1/6`

    ` 2x = 8/3`

    ` x = 8/6`

    `c)`

    ` TH1`

    ` 0,5x – 2 =x +2/3`

    ` 0,5 x – 2 – x – 2/3= 0`

    ` -0,5x – 8/3 = 0`

    ` -0,5 x = 8/3`

    ` x =-16/3`

    `TH2`

    ` 0,5x -2 = -x -2/3`

    ` 0,5x – 2 + x +2/3 = 0`

    ` 1,5x -1/2 = 0`

    ` 1,5x = 1/2`

    ` x = 1/3`

    `d)`

    ` 2x – |x+1| = 1/2`

    Với ` x \ge -1`

    ` => 2x – (x+1) = 1/2`

    ` => 2x – x – 1  = 1/2`

    ` => x -1 = 1/2`

    ` => x= 3/2` ( thỏa mãn )

    Với  `x < -1`

    ` => 2x – (-x-1) = 1/2`

     `=> 2x + x + 1  = 1/2`

    ` => 3x + 1 = 1/2`

    ` => 3x = -1/2`

    ` => x= -1/6` ( ko thỏa mãn )

    Vậy ` x= 3/2`

     

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