Question
If xy=1 , x^2+y^2=2 , find value of x+y
Answer
Apply perfect square formula
(x+y)^2=x^2+2xy+y^2
Substituting xy and x^2+y^2 gives
(x+y)^2=2+2\times 1=4
Taking square roots of both sides gives
x+y = \pm2
If xy=1 , x^2+y^2=2 , find value of x+y
Apply perfect square formula
(x+y)^2=x^2+2xy+y^2
Substituting xy and x^2+y^2 gives
(x+y)^2=2+2\times 1=4
Taking square roots of both sides gives
x+y = \pm2