a, 3.7.23 - 21.(-17)

= 21.23  + 21.17

= 21.(23 + 17)

= 21.40

= 840

b, 7.6.3 - 7.[(-34) + 18)]

= 7.18 - 7.18 + 34.7

= 34.7

= 238

c, 71.64 + 32.(-7) - 13.32

= 71. 32 . 2 - 7.32 - 32. 13

= 32.(71.2 - 7 - 13)

= 32. (142 - 20)

= 32.122

=  3904

d, 13.(23 - 17) - 13.(23 + 17)

= 13.23 - 13.17 - 13.23 - 13.17

= (13.23 - 13.23) - (13.17 + 13.17)

= - 2.13.17

= - 26.17

= -442

e, (29 - 9).(-9) + (-13 - 7).21

= 20.(-9) - 20.21

= -20.(9 + 21)

= -20.30

= - 600

a, \(\left(29-9\right).\left(-9\right)+\left(-13-7\right).21\)

\(=20.\left(-9\right)+\left(-20\right).21\)

\(=-180+\left(-420\right)\)

\(=-600\)

a) (29 – 9). (-9) + (-13 – 7). 21

= 20. (-9) + [- (13 + 7). 21]

= 20. (-9) + (-20). 21

= (-20). 9 + (-20). 21

= (-20). (9 + 21)

= (-20). 30

= - (20. 30)

= - 600.

b) (-157). (127 – 316) – 127. (316 – 157)

= (- 157). 127 + (-157). (-316) + (–127). 316 + (-127). (-157)

= -157. 127 + 157. 316 – 127. 316 + 127. 157

= [- (127. 157) + 127. 157] + (157. 316 – 127. 316)

= 0 + 316. (157 – 127)

= 316. 30

= 9 480.

1)  \(35.18-5.7.28=35.18-35.28=35\left(18-28\right)=-350\)

2)  \(45-5\left(12+9\right)=45-60-45=-60\)

3)  \(24\left(16-5\right)-16\left(24-5\right)=24.16-24.5-16.24+16.5=5\left(16-24\right)=5.8=40\)

4)  \(29\left(19-13\right)-19\left(29-13\right)=29.19-29.13-19.29+19.13=13\left(19-29\right)=-130\)

5)  \(31.\left(-18\right)+31.\left(-81\right)-31=-31.\left(18+81+1\right)=-3100\)

6)  \(\left(-12\right).47+\left(-12\right).52+\left(-12\right)=\left(-12\right)\left(47+52+1\right)=-1200\)

7)  \(13\left(23+22\right)-3\left(17+28\right)=13.45-3.45=45.\left(13-3\right)=450\)

8)  \(-48+48.\left(-78\right)+48.\left(-21\right)=-48\left(1+78+21\right)=-4800\)

a: \(A=21\cdot100-11\cdot100+90\cdot100+100\cdot125\cdot16\)

\(=100\left(21-11+90\right)+100\cdot2000\)

\(=100\left(10+90+2000\right)=2100\cdot100=210000\)

b: \(=\dfrac{5\cdot2^{30}\cdot3^{18}-2^{29}\cdot3^{20}}{5\cdot2^{28}\cdot3^{19}-7\cdot2^{29}\cdot3^{18}}\)

\(=\dfrac{2^{29}\cdot3^{18}\left(5\cdot2-3^2\right)}{2^{28}\cdot3^{18}\left(5\cdot3-7\cdot2\right)}=2\)

1) 35.18 - 5.7.28

= 35.18 - 35.28

= 35.(18 - 28)

= 35.(-10)

= -350

2) 45 - 5.(12 + 9)

= 45 - 5.12 - 5.9

= 45 - 60 - 45

= (45 - 45) - 60

= 0 - 60

= -60

3) 24.(16 - 5) - 16.(24 - 5)

= 24.16 - 24.5 - 16.24 + 16.5

= (24.16 - 16.24) - (24.5 + 16.5)

= 0 - (24.5 + 16.5)

= -24.5 + 16.5

= 5.(-24 + 16)

= 5.(-8)

= -40

4) 29.(19 - 13) - 19.(29 - 13)

= 29.19 - 29.13 - 19.29 + 19.13

= (29.19 - 19.29) + (19.13 - 29.13)

= 0 + (19.13 - 29.13)

= 19.13 - 29.13

= 13.(19 - 29)

= 13.(-10)

= -130

5) 31.(-18) + 31.(-81) - 31

= 31.(-18 - 81 - 1)

= 31.(-100)

= -3100

6) (-12).47 + (-12).52 + (-12)

= (-12).(47 + 52 + 1)

= (-12).100

= -1200

7) 13.(23 + 22) - 3.(17 + 28)

= 13.45 - 3.45

= 45.(13 - 3)

= 45.10

= 450

8) -48 + 48.(-78) + 48.(-21)

= 48.(-1) + 48.(-78) + 48.(-21)

= 48.(-1 - 78 - 21)

= 48.(-100)

= -4800

Cố gắng lên nhé em Hoàng Mai Hoa

1)35.18-5.7.28

= 35 . 18 - 35 . 28

= 35 . ( 18 - 28 )

= 35 . ( - 10 )

= - 350

\(=20.\left(-9\right)+\left(-20\right).21\)

\(=-180+\left(-420\right)\)

\(=-600\)

a) =20.(-9)+(-20).21

=20.(-9)+20.(-21)

=20[(-9)+(-21)]

=20.(-30)

=-600

Cách 1: Theo kiểu dài                       |           Cách 2:Ngắn gọn
a) (29 – 9). (-9) + (-13 – 7). 21          |       a) (29-9) . (-9) + (-13-7) . 21
= 20. (-9) + [- (13 + 7). 21]                 |       =20.(-9)+(-20).21
= 20. (-9) + (-20). 21                          |       =180+(-420)
= (-20). 9 + (-20). 21                          |       =600
= (-20). (9 + 21)                                 |
= (-20). 30                                          |
= - (20. 30)                                         |
= - 600.                                              |

(Chúc bạn học tốt nha~!)