$$
\\left\\{
\\begin{aligned}
x_k=x+k*\frac {b} {gcd(a,b)}\\\\
y_k=y-k\*\frac {a} {gcd(a,b)}
\\end{aligned}
\\right.
$$

$$ \\left\\{ \\begin{aligned} x_k=x+k*\frac {b} {gcd(a,b)}\\\\ y_k=y-k\*\frac {a} {gcd(a,b)} \\end{aligned} \\right. $$

$$
\begin{cases}
x_k=x+k*\frac {b} {gcd(a,b)}\\\\
y_k=y-k*\frac {a} {gcd(a,b)}
\end{cases}
$$

$$ \begin{cases} x_k=x+k\*\frac {b} {gcd(a,b)}\\\\ y_k=y-k\*\frac {a} {gcd(a,b)} \end{cases} $$