Răspuns :
[tex](x - 1)(x + 1) - ( {x}^{2 } + 1) = [/tex]
[tex] = x(x - 1) + (x - 1) - {x}^{2} - 1 = [/tex]
[tex] = {x}^{2} - x + x - 1 - {x}^{2} - 1 = [/tex]
[tex] = - 1 - 1 =[/tex]
[tex] = - 2[/tex]
[tex](x - 1)(x + 1) - ( {x}^{2 } + 1) = [/tex]
[tex] = x(x - 1) + (x - 1) - {x}^{2} - 1 = [/tex]
[tex] = {x}^{2} - x + x - 1 - {x}^{2} - 1 = [/tex]
[tex] = - 1 - 1 =[/tex]
[tex] = - 2[/tex]