帮忙做几题因式分解,1.（x^2+5x+2)(x^2+5x+3）-12 2.（x-2)^3-(y-2)^3-(x-y)^3

帮忙做几题因式分解,1.（x^2+5x+2)(x^2+5x+3）-12 2.（x-2)^3-(y-2)^3-(x-y)^3

设y=x²+5x+2
则原式=y(y+1)-12
=y²+y-12
=(y+4)(y-3)
∴.（x^2+5x+2)(x^2+5x+3）-12=(x²+5x+2+4)(x²+5x+2-3)
=(x+2)(x+3)(x²+5x-1)
2,、设a=x-2 b=y-2 则（x-y)=a-b
∴原式=a³-b³-(a-b)³
=3ab(a-b)
∴原式=3(x-2)(y-2)(x-y)

这两个都要用替换的方法。如果你还不明白,我下午给你过程

1.（x^2+5x+2)(x^2+5x+3）-12 = (x^2+5)^2 + 5(x^2+5x) - 6
= (x^2 + 5x + 6)(x^2 + 5x - 1)
=(x+2)(x+3)(x^2 + 5x -1 )
2.（x-2)^3-(y-2)^3-(x-y)^3 = (x-2-(y-2))((x-2)^2+(x-2)(y-2)+(y-2)^2) - (x-y)...

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1.（x^2+5x+2)(x^2+5x+3）-12 = (x^2+5)^2 + 5(x^2+5x) - 6
= (x^2 + 5x + 6)(x^2 + 5x - 1)
=(x+2)(x+3)(x^2 + 5x -1 )
2.（x-2)^3-(y-2)^3-(x-y)^3 = (x-2-(y-2))((x-2)^2+(x-2)(y-2)+(y-2)^2) - (x-y)^3
=(x-y)[x^2-4x+4 +xy -2x -2y+4 +y^2-4y+4 -x^2+2xy-y^2]
=(x-y)(3xy - 6x - 6y +12)
= 3(x - y)(xy - 2x - 2y + 4)
= 3(x - y)(x(y-2) -2(y-2))
= 3(x - y)(y - 2)(x - 2)

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.（x^2+5x+2)(x^2+5x+3）-12
=（x²+5x)²+5(x²+5x)+6-12
=(x²+5x)²+5(x²+5x)-6
=(x²+5x-2)(x²+5x-3)
（x-2)^3-(y-2)^3-(x-y)^3
=(x-2-y+2)[(x-2)²+(...

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.（x^2+5x+2)(x^2+5x+3）-12
=（x²+5x)²+5(x²+5x)+6-12
=(x²+5x)²+5(x²+5x)-6
=(x²+5x-2)(x²+5x-3)
（x-2)^3-(y-2)^3-(x-y)^3
=(x-2-y+2)[(x-2)²+(x-2)(y-2)+(y-2)²]-(x-y)³
=(x-y)(x²-4x+4+xy-2x-2y+4+y²-4y+4-x²+2xy-y²)
=(x-y)(-6x-6y+3xy+12)
=3(x-y)(xy-2x-2y+4)

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1. (x^2+5x)^2+5(x^2+5x)+6-12
=(x^2+5x+6)(x^2+5x-1)
=(x+2)(x+3)(x^2+5x-1)
2.原式=(x-2-y+2)[(x-2)^2+(y-2)^2+(x-2)(y-2)]-(x-y)^3
=(x-y)[(x-2-x+y)(x-2+x-y)+(y-2)(y-2+x-2)]
=(x-y)(y-2)(2x-y-2+y+x-4)
=3(x-y)(y-2)(x-2)

1. (x^2+5x+2)(x^2+5x+3)-12
= (x^2+5x)^2 +5(x^2+5x) +6 -12
= (x^2+5x)^2 +5(x^2+5x) - 6
= (x^2+5x-1)(x^2+5x+6)
= (x+2)(x+3)(x^2+5x-1).
2. (x-2)^3-(y-2)^3-(x-y)^3
= (x - y)(x^2 + ...

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1. (x^2+5x+2)(x^2+5x+3)-12
= (x^2+5x)^2 +5(x^2+5x) +6 -12
= (x^2+5x)^2 +5(x^2+5x) - 6
= (x^2+5x-1)(x^2+5x+6)
= (x+2)(x+3)(x^2+5x-1).
2. (x-2)^3-(y-2)^3-(x-y)^3
= (x - y)(x^2 + xy - 6x + y^2 - 6y + 12)-(x-y)^3
= (x-y) [ x^2 + xy - 6x +y^2 - 6y + 12 - (x-y)^2 ]
= (x-y) [ 3xy - 6x - 6y + 12 ]
= 3(x-y)(x-2)(y-2).
满意请采纳^_^

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