Let f:R→Rf: \mathbb{R} \to \mathbb{R}f:R→R be a function satisfying f(x+y)=f(x)+f(y)+2xyf(x+y) = f(x) + f(y) + 2xyf(x+y)=f(x)+f(y)+2xy for all real x,yx, yx,y. If f(1)=3f(1) = 3f(1)=3, what is the value of f(4)f(4)f(4)?
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