∇ ( w T x ) = w \nabla(w^{T}x)=w ∇(wTx)=w ∇ ( x T A x ) = ( A + A T ) x \nabla(x^{T}Ax)=(A+A^{T})x ∇(xTAx)=(A+AT)x ∇ 2 ( x T A x ) = ( A + A T ) \nabla^{2}(x^{T}Ax)=(A+A^{T}) ∇2(xTAx)=(A+AT)