建立回归方程:$\hat{y}=a+bx$
$l_{xx}=\sum_{i=1}^n (x_i-\bar{x})^2=$
$\sum_{i=1}^n x_i^2-\frac{1}{n}(\sum_{i=1}^n x_i)^2=$
$l_{xy}=\sum_{i=1}^n (x_i-\bar{x})(y_i-\bar{y})=$
$\sum_{i=1}^n x_iy_i-\frac{1}{n}(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)=$
$l_{yy}=\sum_{i=1}^n (y_i-\bar{y})^2=$
$\sum_{i=1}^n y_i^2-\frac{1}{n}(\sum_{i=1}^n y_i)^2=$