(x+y)(x的平方-xy+y的平方) (x+2)(x+4)-x(x+1)-8 3(x-2)(x+1)-2(x-5)(x-3) x(x的平方-4)-(x+3)(x的平方-3x+2)
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(x+y)(x的平方-xy+y的平方) (x+2)(x+4)-x(x+1)-8 3(x-2)(x+1)-2(x-5)(x-3) x(x的平方-4)-(x+3)(x的平方-3x+2)
(x+y)(x的平方-xy+y的平方) (x+2)(x+4)-x(x+1)-8
3(x-2)(x+1)-2(x-5)(x-3) x(x的平方-4)-(x+3)(x的平方-3x+2)
(x+y)(x的平方-xy+y的平方) (x+2)(x+4)-x(x+1)-8 3(x-2)(x+1)-2(x-5)(x-3) x(x的平方-4)-(x+3)(x的平方-3x+2)
答:
1)立方和公式:
(x+y)(x的平方-xy+y的平方)=x立方+y立方
2)
(x+2)(x+4)-x(x+1)-8
=x^2+6x+8-x^2-x-8
=5x
3)
3(x-2)(x+1)-2(x-5)(x-3)
=3(x^2-x-2)-2(x^2-8x+15)
=3x^2-3x-6-2x^2+16x-30
=x^2+13x-36
4)
x(x的平方-4)-(x+3)(x的平方-3x+2)
=x(x-2)(x+2)-(x+3)(x-2)(x-1)
=(x-2)[(x(x+2)-(x+3)(x-1)]
=(x-2)[x^2+2x-(x^2+2x-3)]
=(x-2)*3
=3x-6
(x+y)(x²-xy+y²)
=x(x²-xy+y²)+y(x²-xy+y²)
=x³-x²y+xy²+x²y-xy²+y³
=x³+y³
(x+2)(x+4)-x(x+1)-8
=(x²+6x+8)-(x&...
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(x+y)(x²-xy+y²)
=x(x²-xy+y²)+y(x²-xy+y²)
=x³-x²y+xy²+x²y-xy²+y³
=x³+y³
(x+2)(x+4)-x(x+1)-8
=(x²+6x+8)-(x²+x)-8
=x²+6x+8-x²-x-8
=5x
3(x-2)(x+1)-2(x-5)(x-3)
=3(x²-x-2)-2(x²-8x+15)
=3x²-3x-6-2x²+16x-30
=x²+13x-36
x(x²-4)-(x+3)(x²-3x+2)
=(x³-4x)-[x(x²-3x+2)+3(x²-3x+2)]
=x³-4x-(x³-3x²+2x+3x²-9x+6)
=x³-7x-x³+3x²-2x-3x²+9x-6
=-6
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