\[y = kx + l;\ \ \ \ A(0; - 3);\ \ B(2;1)\]
\[- 3 = k \cdot 0 + l\]
\[l = - 3 \Longrightarrow y = kx - 3.\]
\[1 = k \cdot 2 - 3\]
\[2k = 4\]
\[k = 2 \Longrightarrow y = 2x - 3.\]
\[Ответ:y = 2x - 3.\]