\(\sqrt{80}-\sqrt{45}+\sqrt{20}\) is equal to:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(3\sqrt{5}\)
Square roots can be added or subtracted only when the number left under the root is the same. Take the largest perfect square out of each root.
\(\sqrt{80}=\sqrt{16\times5}=4\sqrt{5}\)
\(\sqrt{45}=\sqrt{9\times5}=3\sqrt{5}\)
\(\sqrt{20}=\sqrt{4\times5}=2\sqrt{5}\)
\(4\sqrt{5}-3\sqrt{5}+2\sqrt{5}=3\sqrt{5}\)