Consider the equation *x 2 + x – 1 = 0. A calculation shows that its unique positive solution is (51)/2.\left( \sqrt{5} -1 \right)/2.
This equation is equivalent to x (x* + 1) = 1, and hence to x=11+x.x=\frac{1}{1+x}.
Now replace the x in the denominator with 11+x,\frac{1}{1+x}, giving x=11+11+x.x=\frac{1}{1+\cfrac{1}{1+x}}.
There is nothing to stop us repeating the process again and again, suggesting that x can be written as a fraction that "never ends"—what is known as a continued fraction:
x=11+11+11+11+.x=\frac{1}{1+\cfrac{1}{1+\dfrac{1}{1+\cfrac{1}{1+\cdots}}}}.