Answer: C
Begin by dividing 4 on both sides to get [tex]x^{2}[/tex]=81. When a term is squared, that basically means you need to square root the equation. This would equal [tex]\sqrt{x^{2}[/tex]=[tex]\sqrt{81}[/tex]. Square rooting cancels out the x^2, leaving it as x=[tex]\sqrt{81}[/tex]. This also refers to 9,-9. (Keep in mind that when you're square rooting a number, you should always consider both positive and negative.)
