Respuesta :

[tex]x--9=x+9[/tex][tex]x+\text{ -9=x-9}[/tex][tex]x-+9=x-9[/tex][tex]x++9=x+9[/tex]

This is because we know that

[tex]+\times-=-,-\times-=+,-\times+=-\text{ and +}\times+\text{ =+}[/tex]