Question

giải các phương trình sau

Answer 1

Câu 13: 

1: Ta có: \(\sqrt[3]{1000x}-\sqrt[3]{64x}-\sqrt[3]{27x}=15\)

\(\Leftrightarrow10\cdot\sqrt[3]{x}-4\cdot\sqrt[3]{x}-3\cdot\sqrt[3]{x}=15\)

\(\Leftrightarrow3\cdot\sqrt[3]{x}=15\)

\(\Leftrightarrow x=125\)

2) Ta có: \(\sqrt[3]{x-3}+3=x\)

\(\Leftrightarrow\sqrt[3]{x-3}=x-3\)

\(\Leftrightarrow x-3=\left(x-3\right)^3\)

\(\Leftrightarrow\left(x-3\right)^3-\left(x-3\right)=0\)

\(\Leftrightarrow\left(x-3\right)\left(x-2\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=2\\x=4\end{matrix}\right.\)

Answer 2

Câu 12:

Ta có: \(\sqrt[3]{x+7}-3=1\)

\(\Leftrightarrow\sqrt[3]{x+7}=4\)

\(\Leftrightarrow x+7=64\)

hay x=57