The Graph of a Quadratic Function Is Given $f ( x ) = x ^ { 2 } - 6 x + 9$

The graph of a quadratic function is given. Determine the function's equation.
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A) $f ( x ) = x ^ { 2 } - 6 x + 9$
B) $g ( x ) = x ^ { 2 } + 6 x + 9$
C) $h ( x ) = x ^ { 2 } - 3$
D) $j ( x ) = x ^ { 2 } + 3$