Question

Tìm x e Q, biết :

1. \(\left(1-2x\right)^4\) = 81

2. Giá trị tuyệt đối của 2,5 - x = 1,3

3. \(5^x\) + 5 ^{x +2 =} 650

4 . \(\dfrac{3}{8}\) + x - \(\left(-\dfrac{5}{6}\right)\)= \(1\dfrac{1}{3}\)

5.\(-\dfrac{3}{14}\) x + \(\dfrac{5}{7}\) = \(\dfrac{3}{4}\)

Answer 1

1.

\(\left(1-2x\right)^4=81\\ \Rightarrow\left[{}\begin{matrix}1-2x=3\\1-2x=-3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}-2x=2\\-2x=-4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)

Vậy ...

2.

\(\left|2,5-x\right|=1,3\\ \Rightarrow\left[{}\begin{matrix}2,5-x=1,3\\2,5-x=-1,3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1,2\\x=3,8\end{matrix}\right.\)

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3.

\(5^x+5^{x+2}=650\\ 5^x\left(1+5^2\right)=650\\ 5^x\cdot26=650\\ 5^x=25\\ x=2\)

Vậy ...

4, 5 tự làm