# Range ? Of which function!!

Algebra Level 4

$x=\frac { 4\lambda }{ 1+{ \lambda }^{ 2 } }$ $y=\frac { 2-2{ \lambda }^{ 2 } }{ 1+{ \lambda }^{ 2 } }$ $\lambda \in \Re$ If the range of ${ x }^{ 2 }+{ y }^{ 2 }-xy$ is [a,b] , find a+b.

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