câu5 tính thuận tiện a) 14,3 ×4,7+5,3 ×14,3-1,4 ×7,5+7,5 ×4,6 b) 2007×2006-8/2005×2007+1999 c)2005 ×2008-1005/2006 ×2007-1007 d)253×75-161×37+253×25-1

0 bình luận về “câu5 tính thuận tiện a) 14,3 ×4,7+5,3 ×14,3-1,4 ×7,5+7,5 ×4,6 b) 2007×2006-8/2005×2007+1999 c)2005 ×2008-1005/2006 ×2007-1007 d)253×75-161×37+253×25-1”

1. `a)14,3xx4,7+5,3xx14,3-1,4xx7,5+7,5xx4,6`
   `=14,3xx(4,7+5,3)-7,5xx(1,4+4,6)`
   `=14,3xx10-7,5xx6`
   `=143-45`
   `=98`
   `b)(2007xx2006-8)/(2005xx2007+1999)`
   `=(2007xx(2005+1)-8)/(2005xx2007+1999)`
   `=(2007xx2005+2007-8)/(2005xx2007+1999)`
   `=(2007xx2005+(2007-8))/(2005xx2007+1999)`
   `=(2007xx2005+1999)/(2007xx2005+1999)`
   `=1`
   `c)(2005xx2008-1005)/(2006xx2007-1007)`
   `=(2005xx(2007+1)-1005)/((2005+1)xx2007-1007)`
   `=(2005xx2007+2005-1005)/(2005xx2007+2007-1007)`
   `=(2005xx2007+1000)/(2005xx2007+1000)`
   `=1`
   `d)(253xx75-161xx37+235xx25-161xx63)/(100xx47-12xx3,5-5,8:0,1)`
   `=(253xx(25+75)-161xx(37+63))/(4700-42-58)`
   `=(253xx100-161xx100)/(4658-58)`
   `=((253-161)xx100)/4600`
   `=(92xx100)/(46xx100)`
   `=92/46`
   `=2`
   `e)2,5xx20,21xx5xx40xx0,2`
   `=(2,5xx40)xx(5xx0,2)xx20,21`
   `=100xx1xx20,21`
   `=100xx20,21`
   `=2021`
   `f)(10,33+8,27+8,16)-(7,27+6,16+8,33)`
   `=10,33+8,27+8,16-7,27-6,16-8,33`
   `=(10,33-8,33)+(8,27-7,27)+(8,16-6,16)`
   `=2+1+2`
   `=3+2=5`

    

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