Răspuns :
×-1/×+1 +1/×-1
(×-1)(×+1)/(×+1)(×-1) + ×+1/(×-1)(×+1)
(×-1)(×+1)+(×+1)/(×-1)(×+1) = ×+1
(×-1)(×+1)/(×+1)(×-1) + ×+1/(×-1)(×+1)
(×-1)(×+1)+(×+1)/(×-1)(×+1) = ×+1