[tex]\displaystyle\bf\\-\sqrt{m^4n^7}=\\\\=-\sqrt{m^{2\times2}\times n^{3\times2+1}}=\\\\=-\sqrt{m^{2\times2}\times n^{3\times2}\times n}}=\\\\=-\sqrt{\Big(m^2\Big)^2\times \Big(n^3\Big)^2\times n}}=\\\\=-\sqrt{\Big(m^2\times n^3\Big)^2\times n}}=\\\\=\boxed{\bf-m^2n^3\sqrt{n}}[/tex]
