Lời giải:
$B=1+(5+5^2+5^3)+(5^4+5^5+5^6)+....+(5^{88}+5^{89}+5^{90})$

$=1+5(1+5+5^2)+5^4(1+5+5^2)+....+5^{88}(1+5+5^2)$

$=1+(1+5+5^2)(5+5^4+....+5^{88})$

$=1+31(5+5^4+...+5^{88})\not\vdots 31$
Ta có đpcm.

134(-1+51-48)=134*2=268

(-134)+51.134+(-134).48

=134.(-1)+51.134+134.(-48)

=134.[(-1)+51+(-48)]

=134.2

 =268

a) $420-(71+420)$

$=420-71-420$

$=-71$

b) $(35-120)+(120+410-35)$

$=35-120+120+410-35$

$=(35-35)+(-120+120)+410$

$=410$

c) $(320-15+49)-(85-51)$

$=320-15+49-85+51$

$=320+(-15-85)+(49+51)$

$=320+(-100)+100$

$=320$

d) $-(312+59)-(41+400+88)$

$=-312-59-41-400-88$

$=(-312-88)+(-59-41)-400$

$=-400+(-100)-400$

$=-500-400$

$=-900$

e) $(430-731)-(-731+430-56)$

$=430-731+731-430+56$

$=(430-430)+(-731+731)+56$

$=56$

f) $(1352-47)-(53-1000+1352)$

$=1352-47-53+1000-1352$

$=(1352-1352)+(-47-53)+1000$

$=(-100)+1000$

$=1000-100$

$=900$

h) $(-42)-(370+58)-(120-370)$

$=-42-370-58-120+370$

$=(-42-58)+(-370+370)-120$

$=-100-120$

$=-220$

$Toru$

Chịu

Lời giải:
$=-3.125+3.438+125.2-438.3$

$=(3.438-438.3)+(125.2-125.3)$

$=0+125(2-3)=0+125(-1)=0-125=-125$

(-3*2*3)+(125+125)+(438-438)

(-3*2*3)+250

-18+250=232

mong bn đánh giá kq của mik 

(56-27)-(11+28-16)

=29-(39-16)

=29-23

=6

Lời igair:
$(56-27)-(11+27-16)=56-27-11-28+16$

$=(56+16)-(27+11+28)=72-66=6$

Lời giải:

$G=(314+240+470+198)+(251-337)$

 = chẵn + chẵn = chẵn

Vậy $G$ là 1 số chẵn.

Mà $G>2$ nên $G$ là hợp số.