Question Number 131718 by LYKA last updated on 07/Feb/21
$$\boldsymbol{{find}}\:\:\boldsymbol{{and}}\:\boldsymbol{{classify}}\:\boldsymbol{{the}}\:\boldsymbol{{stationary}} \\ $$$$\boldsymbol{{points}}\:\boldsymbol{{of}} \\ $$$$\boldsymbol{{f}}\left(\boldsymbol{{x}}.\boldsymbol{{y}}\right)=\left(\boldsymbol{{x}}−\mathrm{1}\right)^{\mathrm{2}} \left(\boldsymbol{{y}}−\mathrm{2}\right)\left(\boldsymbol{{x}}−\mathrm{2}\boldsymbol{{y}}\right)\left(\boldsymbol{{xy}}+\mathrm{4}\right) \\ $$$$ \\ $$