Answer: 3
Step-by-step explanation:
Let x be the missing base. In this case, base to the power of 2 means this number x times itself will equal 9.
9 = [tex]x^{2}[/tex]
[tex]\sqrt{9}[/tex] = [tex]\sqrt{x^{2} }[/tex] [use square root to cancel the power of 2].
[tex]\sqrt{9}[/tex] = x
x = 3
Check: [tex]3^{2}[/tex] = 3 x 3 = 9
