Bài 1: Tính hợp lí
10) – 1911 – ( 1234 – 1911 )
11) 156 . 72 + 28 . 156
12) 32 . ( – 39 ) + 16 . ( – 22 )
13) – 1945 – ( 567 – 1945 )
14) 184 . 33 + 67 . 184
15) 44 . ( – 36 ) + 22 . ( – 28 )
16) – 1965 – ( 628 – 1965 )
17) 172 . 27 + 73 . 172
18) 66 . ( – 55 ) + 33 . ( – 90 )
19) – 25 . 72 + 25 . 21 – 49 . 25
Bài 2: Tìm x ∈ Z biet
5) 45 – ( x – 9 ) = – 35
6) – 7x – ( – 9 ) = 30
7) x + ( – 3 ) = – 11
8) – 8x – ( – 11 ) = 43
9) 82 – ( 15 + x ) = 72
10) ( – 5 ) + x = 15
11) 2x – ( -17 ) = 15
12) | x – 2 | = 3
13) | x – 3 | – 7 = 13
14) 72 – 3 . | x + 1 | = 9
15) 17 – ( 43 – | x | ) = 45
16) | x + 9 | – 7 = 12
17) 3 | x – 1 | – 5 = 7
18) 2x + 11 – 3 ( x – 9 ) = 0
19) – 15 ( x – 2 ) + 7 ( 3 – x ) = 7
Các bn gúp mk vs
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
Đáp án:
10, -1911- (1234-1911 )=-1911-1234+1911=-1911+1911-1234=0-1234=-1234
11,156.72+28.156=156.(72+28)=156.100=15600
12,32.(-39)+16.(-22)=-1600
13,-1945-(567-1945)=-1945-567+1945=-1945+1945-567=0-567=-567
14,184.33+67.184=184.(33+67)=184.100=18400
15,44.(-36)+22.(-28)=-2200
16,-1965-(628-1965)=-1965-628+1965=-1965+1965-628=0-628=-628
17,172.72+73.172=172.(72+73)=172.145=24940
18,66.(-55)+33.(-90)=-6600
19,-25.72+25.21-49.25=-72.25+25.21-49.25=25.(-72+21)-49.25=-51.25-49.25=25.(-51-49)=-100.25=-2500
B2:
5,45-(x-9)=-35
(x-9)=-35-45
x-9=-80
x =-80+9
x=-71
6,-7x-(-9)=30
-7x+9=30
-7x =30-9
-7x =21
x =21:(-7)
x = -3
7,x+(-3)=-11
x -3 =-11
x =-11+3
x =-8
8,-8x-(-11)=43
-8x+11=43
-8x =43-11
-8x =32
x =32:(-8)
x = -4
9,82-(15+x)=72
15+x =72-82
15+x = -10
x = -10-15
x = -25
10,(-5)+x=15
x=15+5
x=20
11,2x-(-17)=15
2x+17 =15
2x =15-17
2x =-2
x =-2:2
x =-1
12,|x-2|-5=3
x-2 =3+5
x-2 =8
x =8+2
x= 10
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