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\(1)5-(1997-2005)+1997\)
\(=5-1997+2005+1997\)
\(=(-1997+1997)+(5+2005)\)
\(=0+2010\)
\(=2010\)
\(2)4567+(1234-4567)-4\)
\(=4567+1234-4567-4\)
\(=(4567-4567)+(1234-4)\)
\(=0+1230\)
\(=1230\)
\(1+2+3+...+2005+2006=\left[\left(2006-1\right):1+1\right].\left(2006+1\right):2.\)
\(=2006.2007:2\)
\(=2013021\)
\(5+10+...+2000+2005=\left[\left(2005-5\right):5+1\right].\left(2005+5\right):2.\)
\(=401.2010:2\)
\(=403005\)
\(140+136+....+64+60=\left[\left(140-60\right):16+1\right].\left(140+60\right):2.\)
\(=6.200:2\)
\(=600\)
2005.2005-2004.2006
=(2004+1).2005-2004.2006
=2004.2005+2005-2004.2006
=(2004.2005+2004)+1-2004.2006
=2004.(2005+1)+1-2004.2006
=2004.2006+1-2004.2006=1
Ta có:2005*2005-2004*2006=2005*2005-2004*(2005+1)=2005*2005-2004*2005+2004=(2005*2005-2004*2005)+2004
=(2005*(2005-2004))+2004=2005*1+2004=2005+2004=4009
dễ mà : a, 5 - ( 1997 - 2005 ) +1997
= ( 2005 + 5 ) - ( 1997 - 1997 )
= 2010 - 0
= 2010
a, 5 - (1997 -2005 ) + 1997
= 5 - 1997 + 2005 +1997
= (5 + 2005 ) - ( 1997 - 1997)
= 2010 - 0
= 2010
b, 4567 + (1234 - 4567 )-4
= 4567 + 1234 - 4567 -4
= (4567 - 4567 ) + (1234 - 4)
= 0 + 1230
= 1230
c, 173 - ( 36 + 173 ) + [(175 - 27 ) - 175 - ( -36 + 50 )]
= 173 - 36 - 173 + 175 - 27 - 175 - 36 - 50
= ( 173 - 173 ) + (175 - 175 ) - ( 36 + 36 ) - (27 + 50)
= 72 - 77
= -5
d, 3 . (25 : 5 - 14 : 2 ) - 5 . ( 6 : 2)
= 3 (-2) - 5 .3
= 3 ( -2 - 5 )
= 3 . (-7 )
= - 21
\(\frac{2006.2005-1}{2004.2006+2005}\)
\(\Leftrightarrow\)\(\frac{2006.\left(2004+1\right)-1}{2004.2006+2005}\)
\(\Leftrightarrow\frac{2006.2004+2016-1}{2004.2006+2005}\)
\(\Leftrightarrow\frac{2006.2004+2005}{2004.2006+2005}\)
\(=1\)
Tổng dãy số trên là:
( 2006 + 1 ) . [ ( 2006 - 1 ) : 1 +1 ] : 2 = 2013021
Đ/s: 2013021
=5+(-1997)+2005+2005
=-1992+4010
=2018
5 - (1997 - 2005) + 2005
= 5 + 8 + 2005
= 13 + 2005
= 2018