The answers are B. 2 square root of 5 and C. − 2 square root of 5.
\(4 x^{2} -3=77\)
\(4 x^{2} =77+3\)
\(4 x^{2} =80\)
\(x^{2} =80:4\)
\(x^{2} =20\)
\(x= \sqrt{20}\)
\(x= \sqrt{4*5}\)
\(x= \sqrt{4}* \sqrt{5}\)
Since √4 could be either -2 or +2, the solutions are:
\(x=2 \sqrt{5}\) or \(x=-2 \sqrt{5}\)
