[tex]~~~\left(\sqrt 2 + \sqrt 8 \right)^2\\\\=\left(\sqrt 2 \right)^2 + \left(\sqrt 8 \right)^2 +2 \sqrt 2 \sqrt 8\\\\=2+8+2\sqrt{2 \cdot 8}\\\\=10+2\sqrt{16}\\\\=10+2(4)\\\\=10+8\\\\=18[/tex]
