1, 2155– (174 + 2155) + (-68 + 174)
2, -25 . 72 + 25 . 21 – 49 . 25
3, 35(14 –23) – 23(14–35)
4, 8154– (674 + 8154) + (–98 + 674)
5, – 25 . 21 + 25 . 72 + 49 . 25
6, 27(13 – 16) – 16(13 – 27)
7, –1911 – (1234 – 1911)
8, 156.72 + 28.156
9, 32.( -39) + 16.( –22)
10, –1945 – ( 567– 1945)
11, 184.33 + 67.184
12, 44.( –36) + 22.( –28)
Bài 2.Tìm x ∈ Z 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.
9) | x – 3| –7 = 13
10) 72 –3.|x + 1| = 9
11) 17 – (43 – ) = 45
12) 3| x – 1| – 5 = 7
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 < x < 1
18) |x| < 3
19) (x – 3)(x – 5) < 0
20) 2x2 – 3 = 29
21) –6x – (–7) = 25
22) 46 – ( x –11 ) = – 48
Bài 3. Cho biểu thức: A = (-a + b – c) – (- a – b – c)
a) Rút gọn A b) Tính giá trị của A khi a = 1; b = –1; c = –2
Bài 4. Cho biểu thức: A = (–m + n – p) – (–m – n – p)
a) Rút gọn A b) Tính giá trị của A khi m = 1; n = –1; p = –2
Bài 5. Cho biểu thức: A = (–2a + 3b – 4c) – (–2a – 3b – 4c)
a) Rút gọn A
b) Tính giá trị của A khi a = 2012; b = –1; c = –2013
Đáp án:
1, 2155- (174 + 2155) + (-68 + 174)
=2155-174-2155+(-68)+174
=(2155-2155)+(174-174)+(-68)
=0+0+(-68)
=-68
2, -25 . 72 + 25 . 21 – 49 . 25
=25.(-72)+25.21+(-49).25
=25.[(-72)+21+(-49)]
=25.(-100)
=-2500
3, 35(14 –23) – 23(14–35)
=35.14-35.23-23.14+23.35
=(35.14-23.14)+(23.35-35.23)
=14.(35-13)+0
=14.12+0
=168+0
=168
4, 8154-(674+8154)+(-98+674)
=8154-674-8154+(-98)+674
=(8154-8154)+(674-674)+(-98)
=0+0+(-98)
=-98
5, – 25 . 21 + 25 . 72 + 49 . 25
=25.(-21)+25.72+49.25
=25.(-21+72+49)
=25.100
=2 500
6, 27(13 – 16) – 16(13 – 27)
=27.13-27.16-16.13+16.27
=(27.13-16.13)+(27.16-16.27)
=13.(27-16)+0
=13.11+0
=143+0
=143
7, –1911 – (1234 – 1911)
=-1911-1234+1911
=(-1911+1911)-1234
=0-1234
=0+(-1234)
=-1234
8, 156.72 + 28.156
=156.(72+28)
=156.100
=15 600
9, 32.( -39) + 16.( –22)
= 16.2(-39)+16.(-22)
=16.(-78)+16.(-22)
=16.[(-78)+(-22)]
=16.(-100)
=-1600
10, –1945 – ( 567– 1945)
=-1945-567+1945
=(-1945+1945)-567
=0-567
=0+(-567)
=-567
11, 184.33 + 67.184
=184.(33+67)
=184.100
=18 400
12, 44.( –36) + 22.( –28)
=22.2.(-36)+22.(-28)
=22.(-76)+22.(-28)
=22.[(-76)+(-28)]
=22.(-100)
=-2200
Ít điểm quá nên làm bài 1 thoi nha!
#Chúc bạn học tốt!
TL:
$ 1, 2155 – (174 + 2155) + (-68 + 174)$
$ = 2155 – 174 -2155 + ( -68 ) + 174$
$ = ( 2155 – 2155 ) + ( 174 – 174 ) + (-68)$
$ = 0 + 0 + ( -68) = -68$
$ 2, -25 . 72 + 25 . 21 – 49 . 25 $
$ = 25.(-72) + 25.21 + (-49).25$
$ = 25.[(-72)+21+(-49)]$
$ = 25.( -100 )$
$ = -2500$
$ 3, 35( 14 –23 ) – 23( 14–35 )$
$ = 35.14 – 35.23 – 23.14 + 23.35$
$ = ( 35.14-23.14 )+( 23.35-35.23 )$
$ = 14.( 35 – 13 ) + 0$
$ = 14.12 + 0$
$ = 168 + 0 = 168$
$4, 8154-(674+8154)+(-98+674)
= 8154 – 674 – 8154 + (-98)+674
= ( 8154 – 8154 )+( 674 – 674 )+(-98)
= 0 + 0 + (-98) = -98$
$5, – 25 . 21 + 25 . 72 + 49 . 25
= 25 .(-21) + 25.72 + 49.25
= 25. (-21 + 72 + 49)
= 25 . 100 =2500$
$6, 27(13 – 16) – 16(13 – 27)
= 27.13-27.16-16.13+16.27
= (27.13-16.13)+(27.16-16.27)
= 13.( 27 – 16 ) + 0
= 13.11 + 0$
= 143 + 0 = 143
$7, –1911 – (1234 – 1911)
= -1911-1234+1911
= ( -1911 + 1911 ) – 1234
= 0 – 1234
= 0 + ( -1234 )
= – 1234$
$8, 156.72 + 28.156
= 156.(72+28)
= 156.100
= 15600$
$ 9, 32.( -39) + 16.( –22)$
$ = 16.2(-39) + 16.(-22)$
$ = 16.(-78) + 16.(-22)$
$ = 16.[(-78) + (-22)]$
$ = 16.(-100)$
$ = -1600$
$ 10, –1945 – ( 567– 1945)$
$ = -1945-567 + 1945$
$ = (-1945 + 1945) – 567$
$ = 0 – 567$
$ = 0 + (-567) = -567$
$ 11, 184.33 + 67.184$
$ = 184.(33 + 67)$
$ = 184.100 = 18400$
$ 12, 44.( –36) + 22.( –28)$
$ = 22.2.(-36)+22.(-28)$
$ = 22.(-76)+22.(-28)$
$ = 22.[(-76)+(-28)]$
$ = 22. (-100)$
$ = – 2200$
Bài 2: ∅
Bài 3:
$a) A = ( -a – b + c ) – ( – a – b – c )$
$A = -a – b + c + a + b + c$
$A = 2c$
b) Thay c = -2 vào A ta được:
$A = 2. ( -2 )$
$A = -4$
Bài 5:
$a) A = ( –2a + 3b – 4c ) – ( – 2a – 3b – 4c ) = -2a+3b-4c+2a+3b+4c = 3b$
b) Thay $b = -1$ vào A , ta có: $ A = 3.( -1 ) = -3$