2x-｛-3y+[3x-2(3x-y)]},其中x=-1,y=-1/5
=2x+3y+3x-2(3x-y)
=5x+3y-6x+2y
=-x+5y
=-(-1)+5*(-1/5)
=1-1
=0
若2x^ky^k+2与3x^2y^n的和为5x^2y^n,求k、n的值
因为和是单项式,说明前面二个是同类项,则有：
k=2,k+2=n
n=2+2=4
若-3x^m-1y^4与1/3x^2y^n+2是同类项,求m、n
m-1=2
4=n+2
m=3,n=2
若2x^m-1y^2与-x^2y^n是同类项,则(-m)^n=
m-1=2
2=n
m=3,n=2
(-m)^2=(-3)^2=9
计算:2^2004+(-2)^2005
=2^2004-2^2005
=2^2004-2*2^2004
=(1-2)*2^2004
=-2^2004