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x=5/2 3y=1/25 ,求3^(2x+y)
3y=1/25 ,y=1/75
3^(2x+y)=3^(2*5/2+1/75)=3^(376/75)
2008^2-2007*2009
=2008^2-(2008-1)*(2008+1)
=2008^2-(2008^2-1)
=1
123^2-107^2-122*124
=123^2-122*124-107^2
=123^2-(123-1)*(123+1)-107^2
=123^2-(123^2-1)-107^2
=1-107^2
=(1+107)*(1-107)
=108*(-106)
=-11448