1、（3x+y-2)^2
=[(3x+y)-2]^2
=(3x+y)^2-4(3x+y)+4
=9x^2+6xy+y^2-12x-4y+4
2、 (a-2b+1)^2
=[(a-2b)+1]^2
=(a-2b)^2+2(a-2b)+1
=a^2-4ab+4b^2+2a-4b+1
3.
（m+1)^2(m-1)^2
=[（m+1)2(m-1)]^2
=[m^2-1]^2
=m^4-2m^2+1