Inlocuim pe rand in ecuatiile date , pe x= - 1 !
=> a) 3(-1-2) = - 9 => 3*(-3)= - 9 (A) ;
b) 5(-1+4)= 15 => 5*(3) =15 (A) ;
c) 2(-1 -5) -7 = 20 - 1 => 2*(-6) -7 = 19 ⇒ -12-7= 19 (F) pt.ca -19 ≠ 19 !
d) ( -1-3)/2 = -4/2=-2 = 2 (F) pt.ca -2 ≠ 2 !
e) 3[2*(-1)-1]+5=4*(-1) => 3*(-3)+5=-4 adica: -9+5=-4 => -4=-4 (A) ;