Bài 2 Tìm xZ biết :
1) x – 2 = –6
2) –5x – (–3) = 13
3) 15– ( x –7 ) = – 21
4) 3x + 17 = 2
5) 45 – ( x– 9) = –35
6) (–5) + x = 15
7) 2x – (–17) = 15
8) |x – 2| = 3.
13) –12(x – 5) + 7(3 – x) = 5
14) (x – 2).(x + 4) = 0
15) (x –2).( x + 15) = 0
16) (7–x).( x + 19) = 0
17) 5 1 x
18) x 3
19) (x – 3)(x – 5) < 02
9) | x – 3| –7 = 13
10) 72 –3.|x + 1| = 9
11) 17 – (43 – x ) = 45
12) 3| x – 1| – 5 = 7
20) 2x2 – 3 = 29
21) –6x – (–7) = 25
22) 46 – ( x –11 ) = – 48
` 1) ` ` x – 2 = 6 `
` => x = 3 `
` 2) ` ` -5x – (-3) = 13 `
` => -5x = 10 `
` => x = -2 `
` 3) ` ` 15 – (x – 7) = -21 `
` => x – 7 = 36 `
` => x = 43 `
` 4) ` ` 3x + 17 = 2 `
` => 3x = -15 `
` => x = -5 `
` 5) ` ` 45 – (x – 9) = -35 `
` => x – 9 = 80 `
` => x = 89 `
` 6) ` ` (-5) + x = 15 `
` => x = 15 + 5 `
` => x = 20 `
` 7) ` ` 2x-(-17) = 15 `
` => 2x = -2 `
` => x = -1 `
` 8) ` ` |x – 2| = 3 `
` => ` \(\left[ \begin{array}{l}x-2=-3\\x-2=3\end{array} \right.\)
` => ` \(\left[ \begin{array}{l}x=-1\\x=5\end{array} \right.\)
` 9) ` ` |x – 3| – 7 = 13 `
` => |x – 3| = 20 `
` => ` \(\left[ \begin{array}{l}x-3=20\\x-3=-20\end{array} \right.\)
` => ` \(\left[ \begin{array}{l}x=23\\x=-17\end{array} \right.\)
` 10) ` ` 72 – 3.|x + 1| = 9 `
` => 3.|x + 1| = 63 `
` => |x + 1| = 21 `
` => ` \(\left[ \begin{array}{l}x=20\\x=-22\end{array} \right.\)
` 11) ` ` 17 – (43 – x) = 45 `
` => 43 – x = -28 `
` => x = 71 `
` 12) ` ` 3.|x – 1| – 5 = 7 `
` => 3.|x – 1| = 12 `
` => |x – 1| = 4 `
` => ` \(\left[ \begin{array}{l}x=6\\x=-3\end{array} \right.\)
` 13) ` ` -12.(x-5) + 7(3 – x) = 5 `
` => -12x + 60 + 21 – 7x = 5 `
` => -19x + 81 = 5 `
` => -19x = -76 `
` => x = 4 `
` 14) ` ` (x – 2)(x + 4) = 0 `
` => ` \(\left[ \begin{array}{l}x=2\\x=-4\end{array} \right.\)
` 15) ` ` (x – 2)(x + 15) = 0 `
` => ` \(\left[ \begin{array}{l}x=2\\x=-15\end{array} \right.\)
` 16) ` ` (7 – x)(x + 19) = 0 `
` => ` \(\left[ \begin{array}{l}x=7\\x=-19\end{array} \right.\)
1)
x – 2 = –6
x = -6 +2
x = -4
2)
–5x – (–3) = 13
-5x + 3= 13
-5x = 13 – 3
-5x = 10
x = -2
3)
15– ( x –7 ) = – 21
15 – x + 7 = -21
-x = -21 – 15 – 7
-x = -43
x = 43
4)
3x + 17 = 2
3x = 2 – 17
3x = -15
x = -5
5)
45 – ( x– 9) = –35
45 – x + 9 = -35
-x = -35 – 45 – 9
-x = -89
x = 89
6)
(–5) + x = 15
x = 15 + 5
x = 20
7)
2x – (–17) = 15
2x + 17 = 15
2x = 15 – 17
2x = -2
x = -1
8)
|x – 2| = 3.
* TH1:
x-2 = 3
x = 2+3
x = 5
*TH2:
-x + 2 = 3
-x = 3-2
-x = 1
x = -1
13)
–12(x – 5) + 7(3 – x) = 5
-12x +60 + 21 – 7x = 5
-12x – 7x = 5 – 60 – 21
-19x = -76
x = 4
14)
(x – 2).(x + 4) = 0
hoặc x-2=0 hoặc x+4 = 0
x = 2 x = -4
15)
(x –2).( x + 15) = 0
hoặc x-2 = 0 hoặc x+15 = 0
x = 2 x = -15
16)
(7–x).( x + 19) = 0
hoặc 7-x = 0 hoặc x+19 = 0
-x = -7 x = -19
x = 7
9)
| x – 3| –7 = 13
*TH1:
x – 3 – 7 = 13
x = 13 + 3 + 7
x = 23
*TH2:
-x + 3 -7= 13
-x = 13 – 3 +7
-x = 17
x = -17
10) 72 –3.|x + 1| = 9
*TH1:
72 – 3 (x+1) = 9
72 – 3x -3 = 9
-3x = 9 – 72 +3
-3x = -60
x = 20
*TH2:
72 – 3(-x – 1) = 9
72 +3x +3 = 9
3x = 9 – 72 -3
3x =-66
x = -22
11)
17 – (43 – x ) = 45
17 – 43 + x = 45
x = 45 – 17 + 43
x = 71
12)
3| x – 1| – 5 = 7
*TH1:
3(x-1) – 5 = 7
3x -3 -5 =7
3x = 7 + 3 +5
3x = 15
x = 5
*TH2:
3(-x +1) – 5 = 7
-3x + 3 – 5 = 7
-3x = 7 -3 +5
-3x = 9
x = -3
20)
2x^2 – 3 = 29
2x^2 = 32
2x^2 = 2 . 16
x^2 = 16
x = -4 và +4
21)
–6x – (–7) = 25
-6x + 7 = 25
-6x = 25 – 7
-6x = 18
x = -3
22)
46 – ( x –11 ) = – 48
46 -x + 11 = -48
-x = -48 – 46 – 11
-x = -105
x = 105
*CHO MK CTLHN NHÉ BN!!!