Answer
$(x-3)^2-9$
See graph.
Work Step by Step
Step 1. $f(x)=x^2-6x=x^2-6x+9-9=(x-3)^2-9$
Step 2. To graph $f(x)$, start with $y=x^2$, shift 3 units to the left, then shift 9 units down. See graph.
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