Toán Tìm x,y,biết: a)|x−1|+3x=1 b|x−5|+|2x+1|=7 17/07/2021 By Kaylee Tìm x,y,biết: a)|x−1|+3x=1 b|x−5|+|2x+1|=7
a) Th1 : `x – 1 ≥ 0 <=> x ≥ 1` `x-1 + 3x = 1` `x = 1/2 (L)` Th2: `x – 1 < 0 <=> x < 1` `-x+1 + 3x = 1` `x = 0 (TM)` Vậy `x=0` b) Th1 : `x – 5 ≥ 0 ; 2x + 1 ≥ 0 <=> x ≥ 5 `x-5 + 2x + 1 =7` `<=> x = 11/3 (L)` TH2: `x -5 < 0 ; 2x+1 < 0 <=> x < -1/2` `-x+5-2x-1 =7` `x=-1 ( TM)` Th3 : `x-5 ≥ 0 ; 2x + 1 < 0 <=> x ≥ 5 ; x < -1/2 (VN)` Th4 : `x – 5 < 0 ; 2x + 1 ≥ 0 <=> x < 5 ; x ≥ -1/2 <=> -1/2 ≤ x < 5` `-x+5 + 2x+1 = 7` `x = 1` Trả lời
a)|x-1| =1-3x ⇔x-1=1-3x hoặc x-1=3x-1 Nếu x-1=1-3x ⇔x+3x=1+1 ⇔x=1/2 Nếu x-1= 3x-1 ⇔x-3x=-1+1 ⇔-4x=0 ( ko thỏa mãn) vậy x=1/2 b) tương tự ta có 2 TH Trả lời
a)
Th1 : `x – 1 ≥ 0 <=> x ≥ 1`
`x-1 + 3x = 1`
`x = 1/2 (L)`
Th2: `x – 1 < 0 <=> x < 1`
`-x+1 + 3x = 1`
`x = 0 (TM)`
Vậy `x=0`
b)
Th1 : `x – 5 ≥ 0 ; 2x + 1 ≥ 0 <=> x ≥ 5
`x-5 + 2x + 1 =7`
`<=> x = 11/3 (L)`
TH2: `x -5 < 0 ; 2x+1 < 0 <=> x < -1/2`
`-x+5-2x-1 =7`
`x=-1 ( TM)`
Th3 : `x-5 ≥ 0 ; 2x + 1 < 0 <=> x ≥ 5 ; x < -1/2 (VN)`
Th4 : `x – 5 < 0 ; 2x + 1 ≥ 0 <=> x < 5 ; x ≥ -1/2 <=> -1/2 ≤ x < 5`
`-x+5 + 2x+1 = 7`
`x = 1`
a)|x-1| =1-3x ⇔x-1=1-3x hoặc x-1=3x-1 Nếu x-1=1-3x ⇔x+3x=1+1 ⇔x=1/2 Nếu x-1= 3x-1 ⇔x-3x=-1+1 ⇔-4x=0 ( ko thỏa mãn) vậy x=1/2 b) tương tự ta có 2 TH