分解因式①.-a^mb^2m+1+a^m+1b^2m②.3ax^m+1-5ax^m+3ax^m-1 ③.12x^2n+1

①
-a^mb^(2m+1)+a^(m+1)b^(2m)
=a^mb^(2m)*(a-b)
②
3ax^(m+1)-5ax^m+3ax^(m-1)
=ax^(m-1)*(3x²-5x+3)
③
12x^(2n+1)y^(m+2)-20x^(n+1)y^(2m+3)
=4x^(n+1)y^(m+2)*[3x^n-5y^(m+1)]