Answer:
13√7√z
Step-by-step explanation:
[tex]5\times \sqrt{28z} + \sqrt{63z} \\\\5\sqrt{28z}=10\sqrt{7}\sqrt{z}\\\\\sqrt{63z}=3\sqrt{7}\sqrt{z}\\\\=10\sqrt{7}\sqrt{z}+3\sqrt{7}\sqrt{z}\\\\\mathrm{Add\:similar\:elements:}\:10\sqrt{7}\sqrt{z}+3\sqrt{7}\sqrt{z}=\\13\sqrt{7}\sqrt{z}[/tex]
