Đáp án:
8) \(x = \dfrac{3}{4}\)
Giải thích các bước giải:
\(\begin{array}{l}
B2:\\
1)\dfrac{8}{3}:x = \dfrac{{16}}{9}:\dfrac{1}{{50}}\\
\to \dfrac{8}{{3x}} = \dfrac{{800}}{9}\\
\to x = \dfrac{8}{3}:\dfrac{{800}}{9}\\
\to x = \dfrac{3}{{100}}\\
3){\left( {x + 5} \right)^3} = 64\\
\to x + 5 = 4\\
\to x = - 1\\
5){\left( { - \dfrac{1}{3}} \right)^{x - 3}} = \dfrac{1}{{81}}\\
\to {\left( { - \dfrac{1}{3}} \right)^{x - 3}} = {\left( { - \dfrac{1}{3}} \right)^4}\\
\to x - 3 = 4\\
\to x = 7\\
7)\dfrac{{x + 4}}{{20}} = \dfrac{5}{{x + 4}}\\
\to {\left( {x + 4} \right)^2} = 20.5\\
\to {\left( {x + 4} \right)^2} = 100\\
\to \left| {x + 4} \right| = 10\\
\to \left[ \begin{array}{l}
x + 4 = 10\\
x + 4 = - 10
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 6\\
x = - 14
\end{array} \right.\\
2)5 - \left| {3x - 1} \right| = 3\\
\to \left| {3x - 1} \right| = 2\\
\to \left[ \begin{array}{l}
3x - 1 = 2\\
3x - 1 = - 2
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 1\\
x = - \dfrac{1}{3}
\end{array} \right.\\
4)\left| {2x - 3} \right| = 3\\
\to \left[ \begin{array}{l}
2x - 3 = 3\\
2x - 3 = - 3
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 3\\
x = 0
\end{array} \right.\\
6)DK:x \ge - 1\\
2\sqrt {x + 1} = 8\\
\to \sqrt {x + 1} = 4\\
\to x + 1 = 16\\
\to x = 15\\
8){\left( {8x - 1} \right)^{2n + 1}} = {5^{2n + 1}}\\
\to 8x - 1 = 5\\
\to x = \dfrac{3}{4}
\end{array}\)
