计算:1:(2a-3b-c)^2 2:(3y-y-1)(y-3x-1) 3:(2x+y-z)(z-2x+y)

1:(2a-3b-c)^2 =(2a)^2+(-3b)^2+(-c)^2+2(2a)(-3b)+2(2a)(-c)+2(-3b)(-c)
=4a^2+9b^2+c^2-12ab-4ac+6bc
2:(3x-y-1)(y-3x-1)=-[(3x-y)-1][(3x-y)+1]=-[(3x-y)^2-1]
=-(9x^2-6xy+y^2-1)=-9x^2+6xy-y^2+1
3:(2x+y-z)(z-2x+y)=[y+(2x-z)][y-(2x-z)]
=y^2-(2x-z)^2=y^2-4x^2+4xz-z^2