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Ko tính :
\(20092009x201020102010=2010210x200920092009\)
k nha đúng 100%
Ta có:
20092009 x 201020102010
= 2009 x 10001 x 2010 x 100010001 (1)
B = 20102010 x 200920092009
= 2010 x 10001 x 2009 x 100010001 (2)
Từ (1) và (2) => 20092009 x 201020102010 = 20102010 x 200920092009
a, 132 x 99 + 132
= 132 x 99 + 132 x 1
= 132 x ( 99 + 1 )
= 132 x 100 = 13200
b, ( 56 x 27 + 56 x 35 ) : 62
= 56 x ( 27 + 35 ) : 62
= 56 x 62 : 62
= 62 : 62 x 56
= 1 x 56 = 56
c, 2015 x ( 67 + 53 ) - 2005 x ( 53 + 67 )
= 2005 + 10 x 120 - 2005 x 120
= 2005 x 120 - 2005 x 120 + 10
= 2005 x ( 120 - 120 ) + 10
= 2005 x 0 + 10
= 0 + 10 = 10
d, 2009 x 2009 - 2010 x 2008
= 2009 x 2009 - 2009 x 2009
= 2009 x ( 2009 - 2009 )
= 2009 x 0
= 0
e, 4357 x 267 x ( 630 - 315 x 2 )
= 4357 x 267 x ( 630 - 630 )
= 4357 x 267 x 0
= 4357 x 0
= 0
a. 132 x 99 + 132
= 132 x (99 + 1)
= 132 x 100
= 13200
b. (56 x 27 + 56 x 35) : 62
= 56 x (27 + 35) : 62
= 56 x 62 : 62
= 56
c. 2015 x (67 + 53) - 2005 x (53 + 67)
= (2015 - 2005) x (67 + 53)
= 2010 x 120
= 241200
2009 x 17 + 4018 x 41 + 2009 = 2009 x 17 + 2009 x (2 x 41) + 2009
= 2009 x 17 + 2009 x 52 + 2009 x 1
= 2009 x (17 + 52 +1)
= 2009 x 100
= 200900
2009.11-2000-9
=2009.11-(200+9)
=2009.11-2009
=2009.(11-1)
=2009.10
=20090
tik mik nha!!!
2009.11-2000-9
=2009.11-(200+9)
=2009.11-2009
=2009.(11-1)
=2009.10
=20090
Ta có:
2006/2007 + 2007/2008 + 2008/2009 + 2009/2006
= 1 - 1/2007 + 1 - 1/2008 + 1 - 1/2009 + 1 + 3/2006
= (1 + 1 + 1 + 1) - (1/2007 + 1/2008 + 1/2009) + 3/2006
= 4 - (1/2007 + 1/2008 + 1/2009) + 3/2006
Vì 1/2007 < 1/2006
1/2008 < 1/2006
1/2009 < 1/2006
=> 1/2007 + 1/2008 + 1/2009 < 3/2006
=> -(1/2007 + 1/2008 + 1/2009) + 3/2006 > 0
=> 4 - (1/2007 + 1/2008 + 1/2009) + 3/2006 > 4 - 0 = 4
=> 2006/2007 + 2007/2008 + 2008/2009 + 2009/2006 > 4
Ta có:
2006/2007 + 2007/2008 + 2008/2009 + 2009/2006
= 1 - 1/2007 + 1 - 1/2008 + 1 - 1/2009 + 1 + 3/2006
= (1 + 1 + 1 + 1) - (1/2007 + 1/2008 + 1/2009) + 3/2006
= 4 - (1/2007 + 1/2008 + 1/2009) + 3/2006
Vì 1/2007 < 1/2006
1/2008 < 1/2006
1/2009 < 1/2006
=> 1/2007 + 1/2008 + 1/2009 < 3/2006
=> -(1/2007 + 1/2008 + 1/2009) + 3/2006 > 0
=> 4 - (1/2007 + 1/2008 + 1/2009) + 3/2006 > 4 - 0 = 4
=> 2006/2007 + 2007/2008 + 2008/2009 + 2009/2006 > 4
a) 54 x 2009 + 45 x 2009 + 2009
= 54 x 2009 + 45 x 2009 + 2009 x 1
= 2009 x ( 54 + 45 + 1)
= 2009 x 100
= 200900
b) 117 x ( 83 + 17 ) - 17 x ( 17 + 83)
= 117 x 100 - 17 x 100
= 100 x ( 117 - 17 )
= 100 x 100
= 10000
c) 997 x 4 + 997 x 6
= 997 x ( 6 + 4 )
= 997 x 10
= 9970
_HT_