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Explanation:
The translation rule used here is [tex](x,y) \to (x-1, y-1)[/tex]
The x-1 refers to shifting 1 unit to the left, i.e. subtract 1 from the x coordinate.
The y-1 means shift 1 unit down.
So we have
[tex](x,y) \to (x-1,y-1)\\\\(-1,9) \to (-1-1,9-1)\\\\(-1,9) \to (-2,8)[/tex]
