\(\text{Rút gọn:}\)

\(\text{a) }\)\(5\sqrt{\left(-2\right)^4}\)

\(\text{b}\)\(\text{)}\) \(-4.\sqrt{\left(-3\right)^2}\)

\(\text{c)}\) \(\sqrt{\left(3-\sqrt{3}\right)^2}\)

\(\text{d)}\) \(\sqrt{\left(4-\sqrt{17}\right)^2}\)

\(\text{Chứng minh rằng:}\)

\(\text{a) }\) \(9+4\sqrt{5}=\left(\sqrt{5}+2\right)^2\)

\(\text{b)}\) \(\sqrt{9-4\sqrt{5}}-\sqrt{5}=-2\)