Let f(x,y)=x3+2x2y+xy2+y3f(x,y) = x^3 + 2x^2y + xy^2 + y^3f(x,y)=x3+2x2y+xy2+y3. Compute the trace of the Hessian matrix HHH at the point (1,1)(1, 1)(1,1).
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