If we subtract \(\boldsymbol{\vec{B}}\) from \(\boldsymbol{\vec{A}}\) to form the vector difference \(\boldsymbol{\vec{D} = \vec{A} - \vec{B} = \vec{A} + (- \vec{B})}\) , each component of \(\boldsymbol{\vec{D}}\) is equal to the sum of the corresponding components of \(\boldsymbol{\vec{A}}\) and \(\boldsymbol{-\vec{B}}\). The components of \(\boldsymbol{-\vec{B}}\) are \(-\vec{B}_x\) and \(-\vec{B}_y\), so the components of \(\boldsymbol{\vec{D}}\) are \(\vec{D}_x = A_x + (-B_x) = A_x - B_x\) and \(D_y = A_y + (-B_y) = A_y - B_y\).