TL:

2005 x 1999 -1000 x 2005 + 2005

=2005 x (1999 - 1000 + 1)

=2005 x 1000

=2005000

HT!~!

2005 nhân  ( 1999 - 1000 ) = 1002995 đúng thì k sai thì xin lỗi

\(2005\times1999-1000\times2005+2005\)

\(=2005\times1999-1000\times2005+2005\times1\)

\(=2005\times\left(1999-1000+1\right)\)

\(=2005\times1000\)

\(=2005000\)

2005x(1999-1000)=2005x999=2002995

`a)17/7-3/8+4/7-3/5`

`=(17/7+4/7)-(3/8+3/5)`

`=21/7-(15/40+24/40)=3-39/40=120/40-39/40=81/40`

`b)15/11xx2001/2005-3/11xx2001/2005-1/11xx2001/2005`

`=2001/2005xx(15/11-3/11-1/11)`

`=2001/2005xx11/11`

`=2001/2005`

\(248\times2005-2005\times248\)

\(=248\times\left(2005-2005\right)\)

\(=248\times0\)

\(=0\)

248*2005-248*2005=248(2005-2005)=248*0=0

\(248\times2005-2005\times248\)

\(=248\times\left(2005-2005\right)\)

\(=248\times0\)

\(=0\)

1282+2005-3546+4218-454+995

=(1282+4218)+(2005+995)-(3456+454)

=5500+3000-4000

=4500

1282+2005-3546+4218-454+995

=(1282+4218)+(2005+995)-(3456+454)

=5500+3000-4000

=4500

note book

Bạn ơi bằng 4500 nha 

= (1282 + 4218) + (2005 + 995) -( 3546 + 454 )

= 5500 + 3000 -4000

=8500 - 4000 = 4500

2003x2005+200=4016215

2004x2004+199=4016215

= 4016215

=4016215

\(2005-5+5+5+...+5+5\)

\(=2005-5+\left(5+5+...+5\right)\)

\(=2005-5+50\)

\(=2000+50=2050\)

PP/ss: Chắc z ((:

5×(1009+2010)+(-2010)×5

245 x 327 - 245 x 26 - 245 = 245 x (327-26-1) = 245 x 300 = 73500

679+679 x 123 - 679 x 24 = 679 x (1+123-24) = 679 x 100 = 67900

2005 x 1999 - 1000 x 2005 + 2005 = 2005 x (1999-1000+1) = 2005 x 1000 = 2005000

k mk nha