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原题为
1.计算
1)(-2y^3)^2+(-4y^2)^3-[(-2y)^2·(-3y^2)^2]
2) (3x+2)^2-(3x-2)^2+(3x+2)^2·(3x-2)^2
2.化简求值
(x^2+3x)(x-3)-x(x-2)^2+(-x-y)(y-x),其中 x=3,y=2.
人气:494 ℃ 时间:2020-01-04 00:41:06
解答
1.计算
1)(-2y^3)^2+(-4y^2)^3-[(-2y)^2·(-3y^2)^2]
=4y^6-64y^6-[4y^2*9y^4]
=4y^6-64y^6-36y^6
=-96y^6
2) (3x+2)^2-(3x-2)^2+(3x+2)^2·(3x-2)^2
=[(3x+2)+(3x-2)][(3x+2)-(3x-2)]+[(3x+2)(3x-2)]^2
=6x*4+(9x^2-4)^2
=24x+81x^4-72x^2+16
=81x^4-72x^2+24x+16
2.化简求值
(x^2+3x)(x-3)-x(x-2)^2+(-x-y)(y-x),其中 x=3,y=2.
(x^2+3x)(x-3)-x(x-2)^2+(-x-y)(y-x)
=x(x+3)(x-3)-x(x-2)^2-(y+x)(y-x)
=x(x^2-9)-x(x^2-4x+4)-(y^2-x^2)
=x(x^2-9-x^2+4x-4)-y^2+x^2
=x(4x-13)-y^2+x^2
=5x^2-13x-y^2
将x=3,y=2代入,
原式=5*3^2-13*3-2^2
=45-39-4
=2
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