The first term on the right is the original two signals, as expected, followed by the square of the sum, which can be rewritten as ( v 1 + v 2 ) 2 = v 1 2 + 2 v 1 v 2 + v 2 2 {\displaystyle (v_{1}+v_{2})^{2}=v_{1}^{2}+2v_{1}v_{2}+v_{2}^{2}} , where the multiplied signal is obvious. The ellipsis represents all the higher powers of the sum which we assume to be negligible for small signals.