A function f:R→Rf: \mathbb{R} \to \mathbb{R}f:R→R satisfies f(x+y)=f(x)+f(y)+5xyf(x+y) = f(x) + f(y) + 5xyf(x+y)=f(x)+f(y)+5xy. If f(1)=3f(1) = 3f(1)=3, what is f(3)f(3)f(3)?
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