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Question

Tìm x, biết:a) x2 = 10b) $\sqrt x  = 8$c) x3 = - 0,027d) $\sqrt[3]{x} =  - \frac{2}{3}$

datcoder · Accepted Answer

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}$Câu trả lời: a) x2 = 10$\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}$

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