$\sqrt{128}=\sqrt{50}+\sqrt{18}$  

 

$L=\sqrt{128}=\sqrt{64\cdot 2}=\sqrt{64}\cdot \sqrt{2}=8\sqrt{2}$  

 

$P=\sqrt{50}+\sqrt{18}=\sqrt{25\cdot 2}+\sqrt{9\cdot 2}=\sqrt{25}\cdot \sqrt{2}+\sqrt{9}\cdot \sqrt{2}=5\sqrt{2}+3\sqrt{2}=8\sqrt{2}$  

 

$L=P$