An algebra problem by Sakanksha Deo

Algebra Level 2

2 2 2 2 2...... = ? \sqrt{2 \sqrt{2 \sqrt{2 \sqrt{2 \sqrt{2......}}}}} = ?

4 2 \sqrt{2} 2 2 \sqrt{\sqrt{2}} 8

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1 solution

Sakanksha Deo
Mar 1, 2015

Let,

2 2 2 2....... = x \sqrt{2 \sqrt{2 \sqrt{2 \sqrt{2.......}}}} = x

Squaring both sides,

2 2 2 2 2....... = x 2 2 \sqrt{2 \sqrt{2 \sqrt{2 \sqrt{2.......}}}} = x^{2}

2 x = x 2 2x = x^{2}

x = 2 x = \boxed{2}

You can try a different version of this problem here . nested radicals......

A Former Brilliant Member - 6 years, 3 months ago

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I have solved many of your problems...

Sakanksha Deo - 6 years, 3 months ago

I did the same its a nice ques

Kavya Tripathi - 5 years, 11 months ago

How exactly does it become 2x=x squared from all of those roots? Why is it 2x on the left side?

Zyberg NEE - 5 years, 8 months ago

or x=0 which isn't listed, so x=2.

David Holcer - 6 years, 3 months ago

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x can never be 0, since the square root of a positive number is always positive..

Sakanksha Deo - 6 years, 3 months ago

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Touché, thank you for that.

David Holcer - 6 years, 3 months ago

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@David Holcer You are always welcome.....try other questions of my set.

Sakanksha Deo - 6 years, 3 months ago

You're process of solving for x is flawed. Check your answer. Try taking the square root of 2, then the square root of that number, then the square root of that number.... You end up with a number that infinitely approaches 1.

Ski Guy - 6 years, 3 months ago

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I think such infinite series cannot give you exact answers by any process.....its more of a rounding fingure...we just find number to which the answer is most closest to.

Sakanksha Deo - 6 years, 3 months ago

You would be right except it is not asking for the square root of the square root of ... Of the square root of two. There is a 2 2 under every radical. The correct process is to take the square root of two, then double it, then square root, then double, ad infinitum, which gives 2. 2.

Caleb Townsend - 6 years, 2 months ago

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