\[\begin{equation*}
Y_i=\beta_1x_{i1}+\beta_2x_{i2}+\cdots+\beta_px_{ip}+\varepsilon_i,\;\;i=1,2,...,n
\end{equation*}
\]
ili
\[\begin{equation*} Y_i=\beta_0+\beta1x_{i1}+\beta_2x_{i2}+\cdots+\beta_px_{ip}+\varepsilon_i,\;\;i=1,2,...,n \end{equation*} \]