=703-2-289=703-291=412

y=79-37

y=42+179

y=181

\(79-\left(Y-179\right)=37\)

\(-\left(Y-179\right)=37-79\)

\(-\left(y-179\right)=-42\)

\(\Rightarrow y-179=42\Rightarrow y=179+42=221\)

21.300+79.300

300(21+79)

300.100

30000

t nha 

21.(271+29)+79.(271+29)

=(271+29).(21+79)

=300.100

=30000

a) 67+135+33=(67+33)+135=100+135=235

b) 277+13+323+87=(277+323)+(113+87)=600+200=800

c) 29+132 + 237 + 868 + 763=29+(132+868)+(237+763)=29+1000+1000=2029

d) 652 + 327 + 148 + 15 + 73=(652+148)+(327+73)+15=800+400+15=1215

e) 463 + 318 + 137 + 22=(463+137)+(318+22)=600+340=940

g) 189 + 424 +511 + 276 + 55=(189+511)+(424+276)+55=700+700+55=1455

h) (321 +27) + 79=(321+79)+27=400+27=427

i) 185+434+515+266+155=(185+515)+(434+266)+155=700+700+155=1555

k) 168 + 79 + 132=(168+132)+79=300+79=379

l) 29 + 132 + 237 + 868 + 763=29+(132+868)+(237+763)=29+1000+1000=2029

​1. 577 + [ ( -99 ) + 41 ] + ( -618 )

​= 577 + ( -99 ) + 41 + ( -618 )

​= 577 + ( -99 ) + [ 41 + ( -618 ) ]

​= 577 + ( -99 ) + ( -577 )

​= [ 577 + ( -577 ) ] + ( -99 )

= 0 + ( -99 )

= -99

1) 39×51+39×49=39x(51+49)=39x100=3900

2. phân tích 100 thành 50 r lm như câu 1

1. = 39 x (51 + 49)

= 39 x 100

= 3900

2. = 50 x 2 x 31 + 100 x 19

= 100 x 31 + 100 x 19

= 100 x (31 + 19)

= 100 x 50

= 5000

a_n  = n² +1 

a_n = 577 => n² +1 = 577

             => n² = 576=24²

           => n = 24