x = 4 − 1 − 4 − 1 − 4 − 1 − 4 − 1 − x 1 1 1 1 1 1 1 1 Solve for x .
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I did it by brute force, starting from the bottom and evaluating the fraction. It took less than a page.
The verification that 2 is the answer can be done the same way, but is far easier.
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Since x = 4 − 1 − 4 − 1 − 4 − 1 − 4 − 1 − x 1 1 1 1 1 1 1 1 repeatedly substituting this to the x in the continued fraction leads us to the infinite continued fraction x = 4 − 1 − 4 − 1 − 4 − 1 − 4 − 1 − ⋯ 1 1 1 1 1 1 1 1 By passing to the limit, we see that this equation is equivalent to x = 4 − 1 − x 1 1 Solving this equation, we get x x ( x − 1 ) = x 2 − x x 2 − 4 x + 4 = ( x − 2 ) 2 x = 4 − 1 − x 1 1 = 4 − x x − 1 1 = 4 − x − 1 x = 4 ( x − 1 ) − x = 3 x − 4 = 0 = 2