分解因式 1.x²-xy-2y²-x-y 2.a的五次方+a+1 3.x²-3xy

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分解因式 1.x²-xy-2y²-x-y 2.a的五次方+a+1 3.x²-3xy
分解因式 1.x²-xy-2y²-x-y 2.a的五次方+a+1 3.x²-3xy

分解因式 1.x²-xy-2y²-x-y 2.a的五次方+a+1 3.x²-3xy
1.x2-xy-2y2-x-y=x2-y2-y2-(x+y)-xy
=(x+y)(x-y)-(x+y)-xy-y2
=(x+y)(x-y-1)-y(x+y)
=(x+y)(x-2y-1)
2、a^5+a+1 =a^5+a^4+a^3+a^2-a^4-a^3-a^2+a+1
=a^3(a^2+a+1)-a^2(a^2+a+1)+a^2+a+1
=(a^2+a+1)(a^3-a^2+1)
3、x2-3xy=x(x-3y)

1.x²-xy-2y²-x-y=(x²-y²)-(xy+y²)-(x+y)=(x+y)(x-y)-y(x+y))-(x+y)
=(x+y)(x-y-y-1)
=(x+y)(x-2y-1)
a的五次方+a+1
=
3.x²-3xy
=x(x-3y)