[tex]Factor out {b}^{4} [/tex]
[tex] \sqrt{30( {b}^{4} b)} [/tex]
[tex]Rewrite \: {b}^{4} as {b}^{2} {)}^{2} [/tex]
[tex] \sqrt{30(( {b}^{2} {)}^{2} b)} [/tex]
[tex]Reorder 30 and {b}^{2} {)}^{2} [/tex]
Add parentheses
[tex] \sqrt{( {b}^{2} {)}^{2}.(30b) } [/tex]
Pull terms out from under the radical.
[tex] {b}^{2} \sqrt{30b} [/tex]
