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