If $\widehat{\beta}_{0}$ and $\widehat{\beta}_{1}$ are the least-squares estimates for the intercept and slope in a simple linear regression model, show that the least-squares equation $\hat{y}=\hat{\beta}_{0}+\hat{\beta}_{1} x$ always goes through the point $(\bar{x}, \bar{y})$. [Hint: Substitute $\bar{x}$ for $x$ in the least-squares equation and use the fact that $\left.\widehat{\beta}_{0}=\bar{y}-\widehat{\beta}_{1} \bar{x} .\right]$