\[x^{2} - 7x + 6 = 0\]
\[x_{1} + x_{2} = 7;\ \ \]
\[x_{1} \cdot x_{2} = 6 \Longrightarrow x_{1} = 6;\ \ x_{2} = 1.\]
\[x^{2} - 7x + 6 = (x - 6)(x - 1)\]
\[y = x - 6\]