To simplify the square root of 45, we start by factoring 45 into its prime factors:

$45 = 9 \times 5 = 3^2 \times 5$

Now, apply the square root:

$\sqrt{45} = \sqrt{3^2 \times 5} = 3 \sqrt{5}$

Thus, the simplest radical form of $\sqrt{45}$ is:

$3 \sqrt{5}$

Would you like a detailed breakdown, or do you have any questions?

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Here are related questions to deepen understanding:

1. What is the simplest radical form of $\sqrt{50}$?
2. How do we simplify $\sqrt{75}$?
3. Why do we only simplify perfect squares within a square root?
4. How can we simplify $\sqrt{12}$?
5. What steps should we follow to simplify any square root?

Tip: Always look for perfect square factors when simplifying square roots to ensure you reach the simplest form.