（1）4b²-10b+c²-5c+4bc+6=(4b²+c²+4bc)-5(2b+c)+6=(2b+c)²-5(2b+c)+6=(2b+c-2)(2b+c-3)
（2）2x²-xy+3x-y+1
=2x²+3x+1-y(x+1)
=(2x+1)(x+1)-y(x+1)
=(x+1)(2x+1-y)
（3）a²-c²+2ab+b²-d²-2dc
=(a+b)²-(c+d)²=(a+b+c+d)(a+b-C-d)
（4）x²-2xy+y²+2x-2y
=(x-y)²+2(x-y)=(x-y)(x-y+2)
（5）a²-2ab+b²-4c²
=(a-b)²-4c²
=(a-b+2c)(a-b-2c)
（6）已知x+2y+1=0,求x²+xy-2y²+3x+3y+2的值
x²+xy-2y²+3x+3y+2=(x+2y)(x-y)+3x+3y+2=-1（x-y)+3x+3y+2=-x+y+3x+3y+2=2x+4y+2=0