Question

[(3a+b)²-(3a+b)(3a-b)]÷2b

其中a＝-1/3，b＝-2

Answer 1

解题过程如下：

［（3a+b）²-（3a+b）（3a-b）］÷2b

=（3a+b）［（3a+b）-（3a-b）］÷2b

=（3a+b）×2b÷2b

=3a+b

把“a＝-1/3，b＝-2”代入原式得：

3×（-1/3）-2

=-1-2

=-3

最后的计算结果为-3。

Answer 2

[(3a+b)²-(3a+b)(3a-b)]÷2b
={(3a+b)²-[(3a)²-b²]}÷2b
=[(9a²+6ab+b²)-(9a²-b²)]÷2b
=(6ab+2b²)÷2b
=6ab÷2b +2b²÷2b
=3a+b
=3x(-1/3)+(-2)
= -1-2
=-3