9. Simplify $\sqrt{2}+\sqrt{18}$

Step 1 ：The problem is asking to simplify the expression \(\sqrt{2}+\sqrt{18}\).

Step 2 ：First, we need to simplify \(\sqrt{18}\). We know that 18 equals 2 times 9, so \(\sqrt{18} = \sqrt{2 \times 9} = \sqrt{2} \times \sqrt{9} = \sqrt{2} \times 3\).

Step 3 ：So, the expression becomes \(\sqrt{2} + \sqrt{2} \times 3 = \sqrt{2} + 3\sqrt{2}\).

Step 4 ：The expression \(\sqrt{2} + 3\sqrt{2}\) can be simplified further to \(4\sqrt{2}\).

Step 5 ：Final Answer: The simplified form of \(\sqrt{2}+\sqrt{18}\) is \(\boxed{4\sqrt{2}}\).