a/ 215 + [170 -(215+170)]

= 215 +[170 - 215 - 170]

= 215 + 170 - 215 - 170

= (215 - 215) + (170 - 170) = 0

b/ (-371)- [(-371 + 29) - 229]

= (-371) - [-371 + 29 - 229]

= (-371) + 371 - 29 + 229

= (-371 + 371) + (-29 + 229)

= 0 + 200 = 200

c/ (18 + 39) + ( 158 - 39 - 18)

= 18 + 19 + 158 - 39 - 18

= (18 - 18) + (19 - 39) + 158

= 0 - 20 + 158 = 138

d/ 25 + [-37 - 25 + (-63)]

= 25 + [-37 - 25 - 63]

= 25 - 37 - 25 - 63 = (25 - 25) + (37 - 63)

= 0 - 26 = -26

a: =371-271-531+731=100+200=300

b: =-321-28-327+27

=-350-300

=650

c: =-424-371+424+29=-342

d: =-249+248=-1

a)371+(-271)+(-531)+731=300

b)-312+(-327+(-28)+27=650

c)-424+(-371)-(-424)-(-29)=-342

d)-249+197+248+(-197)=-1

e)3+(-5)+(-9)+11+(-13)=-13

g)-8+10+(-12)+14+(-16)+18=6

-5<0<1/63

-101/-100=101/100>1>200/201

1/17>1/27>3/83

135/136=1+(1/136)>1+(1/137)=136/137

-371/459<0<-371/-459

267/-268>-1>-1347/1343

-13/38<-1/3<29/-88

-18/31=\(\frac{-18.10101}{31.10101}=\frac{-181818}{313131}\)

5 > 1/63

101/-100 < 200/201

1/17 > 3/83

135/136 < 136/137

-371/459 < -371/-459

267/-268 > -1347/1343

-13/38 < 29/-88

-18/31 = -181818/313131

a: \(=81\cdot51+49\cdot81=81\cdot100=8100\)

b: \(=371\left(65+25+10\right)=37100\)

a,81*51+49*153-49*72

= 81*51+49*(153-72)

=81*51+49*81

=81*(51+49)

=81*100

=8100

Ta có: \(\dfrac{-371}{-459}=\dfrac{371}{459}\) là một số dương 

=> \(\dfrac{-371}{-459}>\dfrac{-371}{159}\)

[(321 - 797) + (-321 + 697)] - 371 - [1900 + (-371)]

= [321 - 797 - 321 + 697] - 371 - 1900 + 371

= [321 - 321 - 797 + 697] - 371 + 371 - 1900

= -100 - 1900

= -2000.

   Học tốt.

\(\left[\left(321-797\right)+\left(-321+697\right)\right]-371-\left[1900+\left(-371\right)\right]\)

\(=321-797-321+697-371-1900-371\)

\(=\left(321-321\right)-\left(797-697\right)-\left(371-371\right)-1900\)

\(=0-100-0-1900\)

\(=-100-1900\)

\(=-2000\)

[(321 -797)+(-321+697)] -371-[1900+(-371)]

=[321-797-321+697]-371-1900 +371

=(-100)+100-1900

=-1900

= 371 . ( 65 + 14 ) + 629 . 79

= 371 . 79 + 629 . 79

= 79 . ( 371 + 629 ) 

= 79 . 1000

= 79000