ok so according to comments, question is
\(-21\sqrt{27x^{9}}\)
remember that
\(\sqrt{xy}\)=\(\sqrt{x}\) times \(\sqrt{y}\)
and \(\sqrt{yx^{2}}\)=\(x\sqrt{y}\)
so
\(-21\sqrt{27x^{9}}\)=\(-21\sqrt{27}\sqrt{x^{9}}\) = \(-21\sqrt{9}\sqrt{3}\sqrt{x^{2}}\sqrt{x^{2}}\sqrt{x^{2}}\sqrt{x^{2}}\sqrt{x}\)= \(-21(3)\sqrt{3}(x)(x)(x)(x)\sqrt{x}\)=
\(-63x^{4}\sqrt{3}\sqrt{x}\)=\(-63x^{4}\sqrt{3x}\)
