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Hi,
Why does the expression in bracket equal to x when there are infinite roots?
Bunuel
Official Solution:

If \(n\) is an integer greater than 1, what is the value of \(10*\sqrt[n]{10*\sqrt[n]{10*\sqrt[n]{10*\sqrt[n]{...}}}}\), where the given expression extends to an infinite number of roots?

A. \(10\)
B. \(10^{\frac{1}{n}}\)
C. \(10^{\frac{n-1}{n}}\)
D. \(10^{\frac{n}{n-1}}\)
E. \(10^{n}\)


Let \(x=10*\sqrt[n]{10*\sqrt[n]{10*\sqrt[n]{10*\sqrt[n]{...}}}}\)

Now, re-write above as \(x=10*\sqrt[n]{(10*\sqrt[n]{10*\sqrt[n]{10*\sqrt[n]{...})}}}\).

Since the expression extends to an infinite number of roots, then the expression in brackets would also equal to \(x\). Thus we can replace the expression in brackets with \(x\) and rewrite the expression as: \(x=10*\sqrt[n]{x}\)

Take above to the \(n^{th}\) power:

\(x^n=10^n*x\)

\(x^{n-1}=10^n\)

Take \(n-1^{th}\) root:

\(x=10^{\frac{n}{n-1}}\)


Answer: D

We can safely assume that the expression equals x because it's an example of a recursive or self-referential structure. Since the same expression repeats infinitely, we can replace the part inside the brackets with x. This is a common technique when solving problems involving continued roots or similar recursive patterns.

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