就三道简单的因式分解题,
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就三道简单的因式分解题,
(1)x^3-(x^2)y-xy^2+y^3
(2)x^2-8xy+15y^2+2x-6y
(3)已知x^2+4x-1=0,求2x^4+8x^3-4x^2-8x+1的值.
(注:如x^3就是x的三次方)
(1)x^3-(x^2)y-xy^2+y^3
(2)x^2-8xy+15y^2+2x-6y
(3)已知x^2+4x-1=0,求2x^4+8x^3-4x^2-8x+1的值.
(注:如x^3就是x的三次方)
![就三道简单的因式分解题,](/uploads/image/z/18413736-24-6.jpg?t=%E5%B0%B1%E4%B8%89%E9%81%93%E7%AE%80%E5%8D%95%E7%9A%84%E5%9B%A0%E5%BC%8F%E5%88%86%E8%A7%A3%E9%A2%98%2C)
x^3-(x^2)y-xy^2+y^3
=x^3+y^2-xy(x+y)
=(x+y)(x^2-xy+y^2)-xy(x+y)
=(x+y)(x^2-xy+y^2-xy)
=(x+y)(x-y)^2
x^2-8xy+15y^2+2x-6y
=(x-5y)(x-3y)+2(x-3y)
=(x-3y)(x-5y+2)
x^2+4x-1=0
x^2+4x=1
2x^4+8x^3-4x^2-8x+1
=2x^2(x^2+4x)-4x^2-8x+1
=2x^2-4x^2-8x+1
=-2x^2-8x+1
=-2(x^2+4x)+1
=-2+1
= -1
=x^3+y^2-xy(x+y)
=(x+y)(x^2-xy+y^2)-xy(x+y)
=(x+y)(x^2-xy+y^2-xy)
=(x+y)(x-y)^2
x^2-8xy+15y^2+2x-6y
=(x-5y)(x-3y)+2(x-3y)
=(x-3y)(x-5y+2)
x^2+4x-1=0
x^2+4x=1
2x^4+8x^3-4x^2-8x+1
=2x^2(x^2+4x)-4x^2-8x+1
=2x^2-4x^2-8x+1
=-2x^2-8x+1
=-2(x^2+4x)+1
=-2+1
= -1