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

1. 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