(p+q+1+r)(p+q+1-r)+r²-(p+q)²-2(p+q)

Răspuns :

= (p+q+1)^2-r^2+r^2-(p+q)^2-2(p+q)

= (p+q)^2+2(p+q)+1-r^2+r^2-(p+q)^2-2(p+q)

=1