Question

1.Tính x + y :

\(\dfrac{4^x}{2^{x+y}}\) = 8 và \(\dfrac{9^{x+y}}{3^{5y}}\) = 243

2.Tìm x, biết :

a) \(\left(x-1\right)^3\) = 343

b) \(\left(x-2\right)^4\) = 4096

c) \(\left(x-4\right)^2\) = \(\left(x-4\right)^4\)

Answer 1

2.b,

\(\left(x-2\right)^4=4096\\ \left(x-2\right)^4=\left(\pm8\right)^4\\ \Rightarrow\left\{{}\begin{matrix}x-2=8\\x-2=-8\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=10\\x=-6\end{matrix}\right.\)

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câu c:

\(\left(x-4\right)^2=\left(x-4\right)^4\\ \Rightarrow\left\{{}\begin{matrix}x-4=0\\x-4=1\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=4\\x=5\end{matrix}\right.\)

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