X²-3x-4y²+6y=(x-2y)(x+2y)-3(x-2y)=(x-2y)(x+2y-3) 你这题y多了一个平方
a³+5a-5-a²=a(a²+5)-(a²+5)=(a²+5)(a-1)
7ma-20nb-5mb+28na=7a(m+4n)-5b(m+4n)=(m+4n)(7a-5b) 你这题n写成了a
x³-2xy-x²-y² =x³-(x+y)² 你这题应该少了一个y³
(z²-x²-y²)²-4x²y²=(z²-x²-y²-2xy)(z²-x²-y²+2xy)=[z²-(x+y)²][z²-(x-y)²]
=(z-x-y)(z+x+y)(z-x+y)(z+x-y)
x²-6xy-2x+6y+9y²=(x-3y)²-2(x-3y)=(x-3y)(x-3y-2)
m²-2mn+4n-4m+n²+4=(m-n)²-4(m-n)+4=(m-n-2)²
x²-2xy-8x+16+y²+8y=(x-y)²-8(x-y)+16=(x-y-4)²
x²-2x+4y+y²+5=0 求：x,y
x²-2x+1+y²+4y+4=0
(x-1)²+(y+2)²=0
∴x=1 y=-2
a²-c²+2ab-d²+b²-2cd=(a+b)²-(c+d)²=(a+b+c+d)(a+b-c-d)
（x+y）+8（x+y）-20=(x+y+2)(x+y-10)
(p-q)²+3q-3p=(p-q)²-3(p-q)=(p-q)(p-q-3)
(x²-5x)²-24+10x-2x²=(x²-5x)²-2(x²-5x)-24=(x²-5x-6)(x²-5x+4)=(x+1)(x-6)(x-1)(x-4)
(x²+y²)(x²+y²-1)-12=(x²+y²)²-(x²+y²)-12=(x²+y²-4)(x²+y²+3)
(a-b)²-3c²-2ac+2bc=(a-b)²-2c(a-b)-3c²=(a-b-3c)(a-b+c)
-8+(y-x)²-2y+2x=(y-x)²-2(y-x)-8=(y-x-4)(y-x+2)
(x-y)²-3z²-2xz+2yz=(x-y)²-2z(x-y)-3z²=(x-y-3z)(x-y+z)
m²-4mn-2m+4n+4n²-3=(m-2n)²-2(m-2n)-3=(m-2n+1)(m-2n-3)
(a+1)(a+3)(a+5)(a+7)+15=(a²+8a+7)(a²+8a+15)+15=(a²+8a)²+22(a²+8a)+105+15
=(a²+8a)²+22(a²+8a)+120=(a²+8a+10)(a²+8a+12)=(a+2)(a+6)(a²+8a+10)
(x-1)(x+2)(x-3)(x+4)+24=(x²+x-2)(x²+x-12)+24=(x²+x)²-14(x²+x)+24+24
=(x²+x)²-14(x²+x)+48=(x²+x-6)(x²+x-8)=(x-2)(x+3)(x²+x-8)
x²+2+y²-3x-2xy+3y=(x-y)²-3(x-y)+2=(x-y-1)(x-y-2)
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