Using the method of Lagrange multipliers, we have the Lagrangian
with partial derivatives (set equal to 0)
From
and 
, we find that 
. Then substituting into 
, we find
and substituting these into
, we get
So we have two possible critical points,
, which give extreme values of 
and 
, respectively.
with partial derivatives (set equal to 0)
From
and substituting these into
So we have two possible critical points,