Answer:
C
Step-by-step explanation:
Using the rule of radicals
[tex]\sqrt{a}[/tex] × [tex]\sqrt{b}[/tex] ⇔ [tex]\sqrt{ab}[/tex]
Simplifying the radicals
[tex]\sqrt{28}[/tex]
= [tex]\sqrt{4(7)}[/tex]
= [tex]\sqrt{4}[/tex] × [tex]\sqrt{7}[/tex] = 2[tex]\sqrt{7}[/tex]
and
[tex]\sqrt{63}[/tex]
= [tex]\sqrt{9(7)}[/tex]
= [tex]\sqrt{9}[/tex] × [tex]\sqrt{7}[/tex] = 3[tex]\sqrt{7}[/tex]
Hence
2[tex]\sqrt{28}[/tex] + 2[tex]\sqrt{63}[/tex]
= 2(2[tex]\sqrt{7}[/tex] ) + 2(3[tex]\sqrt{7}[/tex] )
= 4[tex]\sqrt{7}[/tex] + 6[tex]\sqrt{7}[/tex]
= 10[tex]\sqrt{7}[/tex] → C
