Question

Tìm x, biết:

a) x² = 10

b) \(\sqrt x  = 8\)

c) x³ = - 0,027

d) \(\sqrt[3]{x} =  - \frac{2}{3}\)

Answer 1

a) x² = 10

\(\begin{array}{l}\sqrt {{x^2}}  = \sqrt {10} \\\left[ {\begin{array}{*{20}{c}}{x = \sqrt {10} }\\{x =  - \sqrt {10} }\end{array}} \right.\end{array}\)

b) \(\sqrt x  = 8\)

\(\begin{array}{l}{\left( {\sqrt x } \right)^2} = {8^2}\\x = 64\end{array}\)

c) x³ = - 0,027

\(\begin{array}{l}\sqrt[3]{{{x^3}}} = \sqrt[3]{{ - 0,027}}\\x = \sqrt[3]{{{{\left( { - 0,3} \right)}^3}}}\\x = 0,3\end{array}\)

d) \(\sqrt[3]{x} =  - \frac{2}{3}\)

\(\begin{array}{l}{\left( {\sqrt[3]{x}} \right)^3} = {\left( { - \frac{2}{3}} \right)^3}\\x =  - \frac{8}{{27}}\end{array}\)