A cura di: Francesco Speciale

${(1/2(x-y)=x+y),(3x=2(x-y)):}$


${(1/2(x-y)=x+y),(3x=2(x-y)):}$; ${(1/2x-1/2y=x+y),(3x=2x-2y):}$;
${(x-y=2x+2y),(x=-2y):}$; ${(-x-3y=0),(x=-2y):}$; ${(2y-3y=0),(x=-2y):}$;
${(-y=0),(x=0):}$; ${(y=0),(x=0):}$.