a)

\(a=2136\times2136=2136\times\left(2134+2\right)=2136\times2134+2136\times2\)

\(b=2134\times2138=2134\times\left(2136+2\right)=2134\times2136+2134\times2\)

Vì \(2136\times2>2134\times2\)     

=> \(a>b\)

b)

=> \(a=b\)\(b=123\times246+77-=123\times\left(245+1\right)+77=123\times245+123+77=123\times245+200\)\(a=245\times124-45=245\times\left(123+1\right)-45=245\times123+245-45=245\times123+200\)

A=123^2 + 54.123 + 77^2 
= 123^2 + 2.123.77 + 77^2 - (154-54).123 
= (123+77)^2 - 100.123 
= 200^2 -12300 
= 40000-12300 
= 27700.

34226 OK

34226 nha

Tính nhanh:

 1+2+3+4+5+6+7+8+9+10

=(1+9)+(2+8)+(3+7)+(4+6)+10+5

=  10  +  10  +  10   + 10  + 10+5

=             50   +   5

=    55

123*45+123*50+123*5

=  123*(45+50+5)

=   123 * 100

=   12300

K mk nha bn

1+2+3+4+5+6+7+8+9+10

= ( 1+10 ) + ( 2+9) + (3+8) + (4+7) + (5+6)

=     11    +      11   +   11    +   11  +    11

=11 x 5 

=55

123 x 45 + 123 x 50 + 123 x 5 

= 123 x ( 45 + 50 +5 )

= 123 x 100

=12300

hok tốt .

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 10 : 2 x 11 = 55

123 x 45 + 123 x 50 + 123 x 5 = 123x ( 45 + 50 + 5) = 123 x 100 = 12300

\(\left(-123\right)+77+\left(-257\right)+23-43=\left(-123+23\right)+\left(77-257\right)-43=-100-180-43=-323\)

(−123)+77+(−257)+23−43

=(−123+23)+(77−257)−43

=−100−180−43

=−323

Bài làm của mik nèe : ^_^

(−123)+77+(−257)+23−43

=(−123+23)+(77−257)−43

=−100−180−43

=−323

Kết quả là : - 323

Tick cho mik nha! :3

Chọn A

− 123 + 77 + − 257 + 23 − 43 = − 123 + 23 + − 257 − 43 + 77 = − 100 + − 300 + 77 = − 400 + 77 = − 323

− 123 + 77 + − 257 + 23 − 43 = − 123 + 23 + − 43 + − 257 + 77 = − 100 + − 300 + 77 = − 400 + 77 = − 323.