问题 解答题

(x2+x+1)(x+2)

(x2﹣x﹣1)(x+1)

(x2+2x﹣1)(x﹣1)

(x2﹣2x+3)(x﹣2)

(a2+3a﹣2)(a+3)

(a2﹣3a+4)(a﹣3)

(a2+4a+1)(2a﹣1)

(a2﹣4a+2)(3a+2)

(2x2﹣3)(x+5)

答案

x3+3x2+3x+2;x3﹣2x﹣1;x3+x2﹣3x+1;x3﹣4x2+7x﹣6;a3+6a2+7a﹣6;a3﹣6a2+13a﹣12;2a3+7a2﹣2a﹣1;3a3﹣10a2﹣2a+4;2x3+10x2﹣3x﹣15.

题目分析:根据多项式乘以多项式的法则:多项式与多项式相乘,先用一个多项式的每一项乘另外一个多项式的每一项,再把所得的积相加,即(a+b)(m+n)=am+an+bm+bn,计算即可.

解:(x2+x+1)(x+2)

=x3+2x2+x2+2x+x+2

=x3+3x2+3x+2;

(x2﹣x﹣1)(x+1)

=x3+x2﹣x2﹣x﹣x﹣1

=x3﹣2x﹣1;

(x2+2x﹣1)(x﹣1)

=x3﹣x2+2x2﹣2x﹣x+1

=x3+x2﹣3x+1;

(x2﹣2x+3)(x﹣2)

=x3﹣2x2﹣2x2+4x+3x﹣6

=x3﹣4x2+7x﹣6;

(a2+3a﹣2)(a+3)

=a3+3a2+3a2+9a﹣2a﹣6

=a3+6a2+7a﹣6;

(a2﹣3a+4)(a﹣3)

=a3﹣3a2﹣3a2+9a+4a﹣12

=a3﹣6a2+13a﹣12;

(a2+4a+1)(2a﹣1)

=2a3﹣a2+8a2﹣4a+2a﹣1

=2a3+7a2﹣2a﹣1;

(a2﹣4a+2)(3a+2)

=3a3+2a2﹣12a2﹣8a+6a+4

=3a3﹣10a2﹣2a+4;

(2x2﹣3)(x+5)

=2x3+10x2﹣3x﹣15.

点评:本题主要考查多项式乘以多项式的法则.注意不要漏项,漏字母,有同类项的合并同类项.

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