题目
Problem
Find the quotient and remainder when x4−3x3+9x2−12x+27 is divided by x2+5.
(3)
题目中文翻译
求 x4−3x3+9x2−12x+27 除以 x2+5 所得的商和余式。
(3)
原卷通用作答要求
Answer all questions. You should use a calculator where appropriate.
You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.
Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.
请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程;仅给出计算器答案而没有过程,不予评分。除非题目另有精度要求,非精确数值答案保留 3 位有效数字,以度为单位的角度保留 1 位小数。
解答
解法一
思路
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按最高次项依次相除。每一步都减去“本次商项乘除式”,最后余式次数必须低于二次。
答题过程
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Let P(x)=x4−3x3+9x2−12x+27. The first quotient term is x2:
=P(x)−x2(x2+5)−3x3+4x2−12x+27.
The next quotient term is −3x:
=(−3x3+4x2−12x+27)−(−3x)(x2+5)4x2+3x+27.
The final quotient term is 4:
(4x2+3x+27)−4(x2+5)=3x+7.
Thus
P(x)=(x2+5)(x2−3x+4)+(3x+7).
The quotient is x2−3x+4 and the remainder is 3x+7.