Find the Lagrange multiplier λ\lambdaλ for maximizing f(x,y)=x+yf(x, y) = x+yf(x,y)=x+y subject to x2+y2=1x^2+y^2=1x2+y2=1.
±1\pm 1±1
±12\pm \frac{1}{\sqrt{2}}±21
±12\pm \frac{1}{2}±21
±2\pm \sqrt{2}±2