a: \(\dfrac{-11}{18}+\dfrac{12}{29}+\dfrac{-7}{18}+\dfrac{2020}{2021}+\dfrac{17}{29}\)

=(-11/18-7/18)+(12/29+17/29)+2020/2021

=2020/2021

b: \(\dfrac{-2}{3}\cdot\dfrac{4}{9}+\dfrac{5}{9}\cdot\dfrac{-2}{3}+\dfrac{4}{3}\)

=-2/3+4/3=2/3

a, (-8)-(-12-8)=(-8)+12+8= [(-8)+8}]+12= 0+12=12

b, 1765-(312+1765)= 1765-312-1765=(1765-1765)-312=0-312=-312

c. (31-12)-(46+31-12)= 31-12+46-31+12= (31-31)+(12-12)+46=0+0+46=46

d, (5674-97)-5674=5674-97-5674=(5674-5674)-97=0-97=-97

e, (-1075)-(29-1075)=(-1075)+29+1075=[(-1075)+1075]+29=0+29=29

g, (18+29)+(158-18-29)=18+29+158-18-29=(18-18)+(29-29)+158=0+0+158=158

h, (13-135+49)-(13+49)=13-135+49-13-49=(13-13)+(49-49)-135=0+0-149=0-149=-149

( 18 + 29 ) + ( 158 − 18 − 29 ) = 18 + 29 + 158 − 18 − 29 = ( 18 − 18 ) + ( 29 − 29 ) + 158 = 0 + 0 + 158 = 158.

\(1+2+3+4+5+...+28+29=\left(1+29\right).29:2=435\)

(1+29)+(2+28)+(3+27)+(4+26)+(5+25)+(6+24)+(7+23)+(8+22)+(9+21)+(10+20)+(11+19)+(12+18)+(13+17)+(14+16)+15

=30+30+30+30+30+30+30+30+30+30+30+30+30+30+15

=30x14+15

=435

 1*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*0*20*21*22*23*24*25*26*27*28*29*30*31*32=0

=0 vì tích có thừa số 0 

a. `306xx 18-306 xx 8=306 xx (18-8) =306 xx 10=3060`

b. `9 xx 9+25xx9 +33 xx18`

`=9 xx9 + 25 xx 9 + 33 xx 2 xx 9`

`=9x (9+25+33xx2)`

`=9 xx (9+25+66)`

`=9 xx 100`

`=900`

a) \(306\cdot18-306\cdot8=306\cdot10=3060\)

b) \(9\cdot9+25\cdot9\cdot33\cdot18=9\cdot9\cdot\left(1+25\cdot33\cdot2\right)=81\cdot1651=133731\)

a ) 10 nha 

b ) 41 ( không chắc lắm )

c ) 10700

d ) 88

e) 454

Bài a,b tự làm:

c,99 x 2014-50 x 2014+2014

=(99-50+1) x 2014

=50 x 2014

=100700

d,(81 x 11):9

=891:9

=99

e,46 x 6+46 x 4

=46 x (4+6)

=46 x 10

=460

2015/2011>1996/1992