Bài 1:
10) - 1911 - ( 1234 - 1911 )
= -1911 + 677
= -1234
11) 156 . 72 + 28 . 156
= 156 . (72 + 28)
= 156 . 100
= 15600
12) 32 . ( - 39 ) + 16 . ( - 22 )
= -1248 - 352
= -1600
13) - 1945 - ( 567 - 1945 )
= -1945 + 1378
= -567
14) 184 . 33 + 67 . 184
= 184 . (33 + 67)
= 184 . 100
= 18400
15) 44 . ( - 36 ) + 22 . ( - 28 )
= -1584 - 616
= -2200
16) - 1965 - ( 628 - 1965 )
= -1965 + 1337
= -628
17) 172 . 27 + 73 . 172
= 172 . (27 + 73)
= 172 . 100
= 17200
18) 66 . ( - 55 ) + 33 . ( - 90 )
= -3630 - 2970
= -6600
19) - 25 . 72 + 25 . 21 - 49 . 25
= 25 . (-72 + 21 - 49)
= 25 . (-100)
= -2500
Bài 2:
5) 45 - ( x - 9 ) = - 35
x - 9 = 45 + 35
x - 9 = 80
x = 80 + 9
x = 89
Vậy x = 89
6) - 7x - ( - 9 ) = 30
-7x = 30 - 9
-7x = 21
x = 21 : (-7)
x = -3
Vậy x = -3
7) x + ( - 3 ) = - 11
x = -11 + 3
x = -8
Vậy x = -8
8) - 8x - ( - 11 ) = 43
-8x = 43 - 11
-8x = 32
x = 32 : (-8)
x = -4
Vậy x = -4
9) 82 - ( 15 + x ) = 72
15 + x = 82 - 72
15 + x = 10
x = 10 - 15
x = -5
Vậy x = -5
10) ( - 5 ) + x = 15
x = 15 + 5
x = 20
Vậy x = 20
11) 2x - ( -17 ) = 15
2x = 15 - 17
2x = -2
x = -2 : 2
x = -1
Vậy x = -1
12) | x - 2 | = 3
\(\left[ \begin{array}{l}x-2=3\\x-2=-3\end{array} \right.\)
\(\left[ \begin{array}{l}x=3+2\\x=-3+2\end{array} \right.\)
\(\left[ \begin{array}{l}x=5\\x=-1\end{array} \right.\)
Vậy x = 5 hoặc x = -1
13) | x - 3 | - 7 = 13
|x - 3| = 13 + 7
|x - 3| = 20
\(\left[ \begin{array}{l}x-3=20\\x-3=-20\end{array} \right.\)
\(\left[ \begin{array}{l}x=20+3\\x=-20+3\end{array} \right.\)
\(\left[ \begin{array}{l}x=23\\x=-17\end{array} \right.\)
Vậy x = 23 hoặc x = -17
14) 72 - 3 . | x + 1 | = 9
3 . | x + 1 | = 72 - 9
3 . | x + 1 | = 63
| x + 1 | = 63 : 3
| x + 1 | = 21
\(\left[ \begin{array}{l}x+1=21\\x+1=-21\end{array} \right.\)
\(\left[ \begin{array}{l}x=21-1\\x=-21-1\end{array} \right.\)
\(\left[ \begin{array}{l}x=20\\x=-22\end{array} \right.\)
Vậy x = 20 hoặc x = -22
15) 17 - ( 43 - | x | ) = 45
43 - | x | = 17 - 45
43 - | x | = -28
|x| = 43 + 28
|x| = 71
\(\left[ \begin{array}{l}x=71\\x=-71\end{array} \right.\)
Vậy x = 71 hoặc x = -71
16) | x + 9 | - 7 = 12
|x + 9| = 12 + 7
|x + 9| = 19
\(\left[ \begin{array}{l}x+9=19\\x+9=-19\end{array} \right.\)
\(\left[ \begin{array}{l}x=19-9\\x=-19-9\end{array} \right.\)
\(\left[ \begin{array}{l}x=10\\x=-28\end{array} \right.\)
Vậy x = 10 hoặc x = -28
17) 3 | x - 1 | - 5 = 7
3 | x - 1 | = 7 + 5
3 | x - 1 | = 12
|x - 1| = 12 : 3
|x - 1| = 4
\(\left[ \begin{array}{l}x-1=4\\x-1=-4\end{array} \right.\)
\(\left[ \begin{array}{l}x=4+1\\x=-4+1\end{array} \right.\)
\(\left[ \begin{array}{l}x=5\\x=-3\end{array} \right.\)
Vậy x = 5 hoặc x = -3
18) 2x + 11 - 3 ( x - 9 ) = 0
2x + 11 = 0 + 3 ( x - 9 )
2x + 11 = 3 ( x - 9 )
2x + 11 = 3x - 3 . 9
2x + 11 = 3x - 27
2x - 3x = -27 - 11
-x = -38
x = 38
Vậy x = 38
19) - 15 ( x - 2 ) + 7 ( 3 - x ) = 7
-15x - (-15) . 2 + 7 . 3 - 7x = 7
-15x + 30 + 21 - 7x = 7
-15x - 7x = 7 - 30 - 21
-22x = -44
x = -44 : (-22)
x = 2
Vậy x = 2
