Then, $i = j + 9$. We also need to change the limits of the summation. When $i = 1$, we have $j = 1 - 9 = -8$. When $i = n$, we have $j = n - 9$. So, the new summation is:
$$\sum_{j=-8}^{n-9} (n - (j + 9))^2$$
Now, let's simplify the expression inside the
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