(1)根据所给的这一组数据,得到5个点的坐标(3,2),(5,3),(6,3),(7,4),(9,5)把这几个点的坐标在直角坐标系中描出对应的点,得到散点图. (2)==6, ==3.4,
5 | | i=1 | x | 2i | =32+52+62+72+92=200,
5 | | i=1 | xiyi=3×2+5×3+6×3+7×4+9×5=112,
| b | =5 | | i=1 | xiyi-5 | 5 | | i=1 | x | 2i | -52 | ==0.5,
| a | =- | b | =3.4-0.5×6=0.4, ∴回归直线方程是 | y | =0.5x+0.4. (3)当 | y | =1时,1=0.5x+0.4⇒x=1.2. 要达到1万元的利润额,销售额大约为1.2万元. |