tìm x biết
a, 2/3x : 2 = 1/3
b, (x+1/2) = 8
c, 2,6 : (2x) = 2/3.0,25
d, |2x-1| = 3x+2
tìm x biết a, 2/3x : 2 = 1/3 b, (x+1/2) = 8 c, 2,6 : (2x) = 2/3.0,25 d, |2x-1| = 3x+2
By Eden
By Eden
tìm x biết
a, 2/3x : 2 = 1/3
b, (x+1/2) = 8
c, 2,6 : (2x) = 2/3.0,25
d, |2x-1| = 3x+2
Đáp án:
a, `2/3x : 2 = 1/3`
`=> 2/3x = 1/3 .2`
`=> 2/3x = 2/3`
`=> x = 2/3 : 2/3`
`=> x = 2/3 .3/2`
`=> x =1`
b, (x+1/2) = 8
`=> x = 8 -1/2`
`=> x = 15/2
c, 2,6 : (2x) = 2/3.0,25
`=> 2,6 : 2x = 2/3 . 1/4`
`=> 2,6 : 2x = 1/3 .1/2`
`=> 2,6 : 2x = 1/6`
`=> 2x = 1/6 : 2,6`
`=> 2x = 5/78`
`=> 2x = 5/78 : 2`
`=> x = 5/156`
d,` |2x-1| = 3x+2`
`3x + 2 ≥ 0 -> 3x ≥ -2 -> x ≥ -2/3`
TH1 `=> 2x -1 = 3x +2`
`=> 2x – 3x = 2+1`
`=> -x = 3`
`=> x =-3`
`TH2 = -2x + 1 = 3x +2`
`=> `-2x- 3x= 2-1`
`=> -5x = 1`
`=> x = -1/5`
mong ctlhn aạ~~
*Lời giải :
a) 2/3x : 2 = 1/3
-> 2/3x = 2/3
-> x = 1
Vậy x = 1
b) (x + 1/2) = 8
-> x = 8 – 1/2
-> x = 15/2
Vậy x = 15/2
c) 2,6 : 2x = 2/3 . 0,25
-> 2,6 : 2x = 1/6
-> 2x = 78/5
-> x = 39/5
Vậy x = 39/5
d) |2x – 1| = 3x + 2 (1)
Điều kiện : 3x + 2 ≥ 0 -> 3x ≥ -2 -> x ≥ -2/3
Từ đó (1) sẽ trở thành :
|2x – 1| = |3x + 2|
TH1 : 2x – 1 = 3x + 2
-> 2x – 3x = 1 + 2
-> -x = 3
-> x = -3 (không thỏa mãn)
TH2 : 2x – 1 = -3x – 2
-> 2x + 3x = 1 – 2
-> 5x = -1
-> x = -1/5 (thỏa mãn)
Vậy x = -1/5