Question

root 45 - 3 root 20 + 4 root 5

Answer 1

$$\begin{gathered} \sqrt{45}-3\sqrt{20}+4\sqrt{5} \\ =\sqrt{3\times 3\times 5}-3\sqrt{2\times 2\times 5}+4\sqrt{5} \\ =3\sqrt{5}-3\times 2\sqrt{5}+4\sqrt{5} \\ =3\sqrt{5}-6\sqrt{5}+4\sqrt{5} \\ =\left(3-6+4\right)\sqrt{5} \\ =\sqrt{5} \end{gathered}$$