What is the definition of root?

Algebra Level 3

240 + 240 + 240 + = ? \sqrt{ 240 + \sqrt{ 240 + \sqrt{ 240 + \ldots } } } =?


The answer is 16.

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2 solutions

Md Mehedi Hasan
Nov 19, 2017

Let, x = 240 + 240 + 240 + x = 240 + x x 2 = 240 + x x 2 x 240 = 0 x=\sqrt{ 240 + \sqrt{ 240 + \sqrt{ 240 + \ldots } } } \\ \Rightarrow x=\sqrt{240+x}\\ \Rightarrow x^2=240+x\\ \Rightarrow x^2-x-240=0

Solving we get x = 16 , 15 x=16,-15

But x 15 x\neq-15 so x = 240 + 240 + 240 + = 16 x=\sqrt{ 240 + \sqrt{ 240 + \sqrt{ 240 + \ldots } } }=\boxed{16}

Munem Shahriar
Nov 18, 2017

Suppose 240 + 240 + 240 + = x \sqrt{ 240 + \sqrt{ 240 + \sqrt{ 240 + \ldots } } } =x

Now,

x = 240 + x x = \sqrt{240 + x}

x = 240 + 16 x = \sqrt{240 + 16}

16 = 256 16 = \sqrt{256}

16 = 16 16 = 16

Hence x = 16 x = 16

Can we solve it by factoring quadratic equations?

Saksham Jain - 3 years, 6 months ago

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