For an algebraic proof of this result, start with the equation 0 = − 1 ⋅ 0 = − 1 ⋅ {\displaystyle 0=-1\cdot 0=-1\cdot } The first equality follows from the above result.
Para demostrar alxebricamente o resultado comézase coa ecuación 0 = − 1 ⋅ 0 = − 1 ⋅ {\displaystyle 0=-1\cdot 0=-1\cdot } Esta ecuación séguese do resultado anterior.