Gọi x1, x2 là hai nghiệm củ...

D

- Hướng dẫn giải

Ta có: \({4^x} - {8.2^x} + 4 = 0\)

\(\Leftrightarrow {\left( {{2^x}} \right)^2} - 8.\left( {{2^x}} \right) + 4 = 0\)

\( \Leftrightarrow \left[ \begin{array}{l}{2^x} = 4 + 2\sqrt 3 \\{2^x} = 4 - 2\sqrt 3 \end{array} \right. \)

\(\Leftrightarrow \left[ \begin{array}{l}x = {\log _2}\left( {4 + 2\sqrt 3 } \right)\\x = {\log _2}\left( {4 - 2\sqrt 3 } \right)\end{array} \right.\)

Khi đó

\(P = {x_1} + {x_2} \)\(\,= {\log _2}\left( {4 + 2\sqrt 3 } \right) + {\log _2}\left( {4 - 2\sqrt 3 } \right) \)\(\,= {\log _2}\left( {16 - 12} \right) = 2\)