We can see that $(-1,1) + (1,2) = (0,3)$ and if we multiply this by $1/3$, we get $(0,1)$. So, we have $(0,1) = 1/3 \cdot (-1,1) + 1/3 \cdot (1,2)$. Similarly, we can see that $(1,2) - 2 \cdot (-1,1) = (3,0)$ and if we multiply this by $1/3$, we get $(1,0)$. So,
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