a: Sửa đề: \(\sqrt{x^2-12x+36}+\sqrt{\left(-25\right)\cdot\left(-x^2\right)}\)
\(=\sqrt{\left(x-6\right)^2}+\sqrt{25x^2}\)
=|x-6|+|5x|
=x-6+5x=6x-6
b: \(=\sqrt{10+4\left(\sqrt{2}-1\right)}-5-\sqrt{2}\)
\(=\sqrt{6+4\sqrt{2}}-5-\sqrt{2}\)
\(=2+\sqrt{2}-5-\sqrt{2}=-3\)