Infinite Fractions - 1

Algebra Level 3

2 2 + 12 ( 2 2 + 12 ( 2 2 + ) ) = ? \cfrac { 2 }{ 2+12\left( \cfrac { 2 }{ 2+12\left( \cfrac { 2 }{ 2+\ddots } \right) } \right) } =?

Note: Round answer to 3 decimal places.


The answer is 0.333.

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1 solution

Let x \color{#3D99F6}{x} equal to the given expression.

2 2 + 12 ( 2 2 + 12 ( 2 2 + ) ) = x \Rightarrow \frac { 2 }{ 2+12\left( \frac { 2 }{ 2+12\left( \frac { 2 }{ 2+\dots } \right) } \right) } =\color{#3D99F6}{x}

x = 2 2 + 12 ( x ) \color{#3D99F6}{x}=\dfrac{2}{2+12(\color{#3D99F6}{x})}

x = 2 2 ( 1 + 6 x ) \color{#3D99F6}{x}=\dfrac{2}{2(1+6\color{#3D99F6}{x})}

x = 1 1 + 6 x \color{#3D99F6}{x}=\dfrac{1}{1+6\color{#3D99F6}{x}}

6 x 2 + x 1 = 0 6\color{#3D99F6}{x}^2+\color{#3D99F6}{x}-1=0

By the Quadratic formula ,

x = 0.333 , 0.5 \color{#3D99F6}{x}=0.333, -0.5

Because given expression consist only positive terms.Hence, neglecting 0.5 -0.5 .

2 2 + 12 ( 2 2 + 12 ( 2 2 + ) ) = 0.333 \Rightarrow \frac { 2 }{ 2+12\left( \frac { 2 }{ 2+12\left( \frac { 2 }{ 2+\dots } \right) } \right) } = \color{#3D99F6}{0.333}

Nice solution !!

Akshat Sharda - 5 years, 4 months ago

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