To subtract \( \sqrt{75} - \sqrt{45} \), we can simplify each square root first.
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Simplify \( \sqrt{75} \): \[ \sqrt{75} = \sqrt{25 \times 3} = \sqrt{25} \times \sqrt{3} = 5\sqrt{3} \]
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Simplify \( \sqrt{45} \): \[ \sqrt{45} = \sqrt{9 \times 5} = \sqrt{9} \times \sqrt{5} = 3\sqrt{5} \]
Now we can rewrite the original expression: \[ \sqrt{75} - \sqrt{45} = 5\sqrt{3} - 3\sqrt{5} \]
Since \( 5\sqrt{3} \) and \( 3\sqrt{5} \) are not like terms, we cannot simplify it further.
Thus, the difference is: \[ \boxed{5\sqrt{3} - 3\sqrt{5}} \]