计算:(1)(-3x2y3z)3÷9x3y5÷x3-(-3x2y)2(2)化简求值:(x-2)(x2-6x-9)-x(x-3)(x-5),其中x=13.-数学

题目简介

计算:(1)(-3x2y3z)3÷9x3y5÷x3-(-3x2y)2(2)化简求值:(x-2)(x2-6x-9)-x(x-3)(x-5),其中x=13.-数学

题目详情

计算:
(1)(-3x2y3z)3÷9x3y5÷x3-(-3x2y)2
(2)化简求值:(x-2)(x2-6x-9)-x(x-3)(x-5),其中x=
1
3
题型:解答题难度:中档来源:不详

答案

(-3x2y3z)3÷9x3y5÷x3•(-3x2y)2
=-27x6y9z3÷9x3y5÷x3•9x4y2
=-3x3y4z3÷x3•9x4y2
=-3y4z3•9x4y2
=-27x4y6z3;

(2)(x-2)(x2-6x-9)-x(x-3)(x-5)
=x3-6x2-9x-2x2+12x+18-x(x2-8x+15)
=x3-8x2+3x+18-x3+8x2-15x
=-12x+18,
当x=class="stub"1
3
时,原式=-12×class="stub"1
3
+18=-4+18=14.

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