Answer:
2[tex]\sqrt{21}[/tex]
Step-by-step explanation:
Using the rule of radicals
[tex]\sqrt{a}[/tex] × [tex]\sqrt{b}[/tex] ⇔ [tex]\sqrt{ab}[/tex]
[tex]\sqrt{84}[/tex] = [tex]\sqrt{4(21)}[/tex] = [tex]\sqrt{4}[/tex] × [tex]\sqrt{21}[/tex] = 2[tex]\sqrt{21}[/tex]
