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Question:

What is \(4 \sqrt{45} - 7 \sqrt{5}\)?

A \(5 \sqrt{5}\)
explanation

To subtract these radicals together their radicals must be the same:
\([4 \sqrt{45} - 7 \sqrt{5}] \) = \(4 \sqrt{ 3^2 \times 5 } - 7 \sqrt{5} \) = \(4 \times 3 \sqrt{5} - 7 \sqrt{5} = 5 \sqrt{5} \)