A function f:R→Rf: \mathbb{R} \to \mathbb{R}f:R→R satisfies f(x+y)=f(x)+f(y)+2xyf(x+y) = f(x) + f(y) + 2xyf(x+y)=f(x)+f(y)+2xy. If f(1)=2f(1) = 2f(1)=2, find f(n)f(n)f(n) for any positive integer nnn.
n2+nn^2 + nn2+n
n2n^2n2
2n22n^22n2
n2+1n^2 + 1n2+1