Advertisements (Quảng cáo)
Tìm x, biết :
a) \(\sqrt[3]{x} = 6\); b) \(\sqrt[3]{{2x}} = 4\);
c) \(\sqrt[3]{{2x – 5}} = 3\).
Advertisements (Quảng cáo)
Sử dụng công thức: \(\sqrt[3]{x} = a \Leftrightarrow x = {a^3}.\)
\(\begin{array}{l}a)\;\sqrt[3]{x} = 6\\ \Leftrightarrow x = {6^3}\\ \Leftrightarrow x = 216.\end{array}\) \(\begin{array}{l}b)\;\sqrt[3]{{2x}} = 4\\ \Leftrightarrow 2x = {4^3}\\ \Leftrightarrow 2x = 64\\ \Leftrightarrow x = 32.\end{array}\) \(\begin{array}{l}c)\;\sqrt[3]{{2x – 5}} = 3\\ \Leftrightarrow 2x – 5 = {3^3}\\ \Leftrightarrow 2x = 32\\ \Leftrightarrow x = 16.\end{array}\)