1)12.194+6.437.2+3,369.4=12.194+12.437+12,369=12.(194+437+369)=12x1000=12000

2)1+5+9+13+........+57+61+65.2-26

3)8.9.14+6.17.12+19.4.18=72x14+72x17+19.72=72x(14+17+19)=72x50=3600

4)1+2-3-4-5+6-7-8+9+994-995-996+997+998

5)1994.19931993-1993.19941994=0

nhanh lên gấp lắm .nhanh lên nhen

1) 12000

3) 3600

5)0

Tính

A=12.194+6.437.2+3.369.4

B=1+5+9+13+...+57+61+65.2-26

Giải:A=12.194 + 6.2.437 + 3.4.369

=12.194+12.437+12.369

=12.(194+437+369)

=12.1000=12000

B=1+5+..............+57+61+65.2-26

=(1+61)+(5+57)+...........+(29+33) + 130-26

=62+62+...........+62+104

=62 x 8 + 104

=496+104=600

Vậy................

Ko phai day la so tren gach ngang so duoi

neu muon thi rut gon A/B

M = 1 + (2 -  3 - 4 + 50 + .... + (994 - 995 - 996  + 997 ) + 998

M = 0 + 0 + .... + 0  + 1 + 998 = 999

998

1+ (2-3-4+5)+(6-7-8+9)+.....+(994-995-996+997)+998

1+0+0+......+0+998

=999

1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 + 10 - ... + 994 - 995 - 996 + 997 + 998

= ( 1 + 998 ) + ( 2 + 997 ) + ( - 3 - 996 ) + ( - 4 - 995) + ( 5 + 994 ) + ( 6 + 993 ) +... + ( 499 + 500)

= 999

1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + ... + 994 - 995 - 996 + 997 + 998 

= 1 + (2 - 3 - 4  + 5) + (6 - 7 - 8 + 9) + ... + (994 - 995 - 996 + 997) + 998 

= 1  +      0             +          0          + .... +                   0             + 998 

=  1  +   998 

= 999 

\(A=1-2-3+4+5-6-7+8...+993-994-995+996+997\)

\(A=\left(1-2-3+4\right)+\left(5-6-7+8\right)...+\left(993-994-995+996\right)+997\)

\(A=0+0+...+0+997=997\)

hhadsgbdáh

C=1+2-3-4+5+6-7-8+9+...+994-995-996+997+998

C=1+(2-3-4+5)+(6-7-8+9)+...+(994-995-996+997)+998

C = 1+0+0+...+0+998

C = 999

1+2-3-4+5+6-7-8+9+...+994-995-996+997+998

=(2-3-4+5)+...+(994-995-996+997)+998+1

=0+...+0+999=999