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2-1-3-a-1-b-1-c-1-d-a-b-c-d-Z-What-s-b-




Question Number 70885 by naka3546 last updated on 09/Oct/19
(2)^(1/3)   = a + (1/(b + (1/(c + (1/(d + …))))))  a, b, c, d  ∈ Z^+   What′s  b  ?
$$\sqrt[{\mathrm{3}}]{\mathrm{2}}\:\:=\:{a}\:+\:\frac{\mathrm{1}}{{b}\:+\:\frac{\mathrm{1}}{{c}\:+\:\frac{\mathrm{1}}{{d}\:+\:\ldots}}} \\ $$$${a},\:{b},\:{c},\:{d}\:\:\in\:\mathbb{Z}^{+} \\ $$$${What}'{s}\:\:{b}\:\:? \\ $$
Answered by MJS last updated on 09/Oct/19
the continued fraction of (2)^(1/3)  is non+periodic  ⇒ just calculate it  a=1  b=⌊(1/( (2)^(1/3) −1))⌋=⌊(4)^(1/3) +(2)^(1/3) +1⌋=3
$$\mathrm{the}\:\mathrm{continued}\:\mathrm{fraction}\:\mathrm{of}\:\sqrt[{\mathrm{3}}]{\mathrm{2}}\:\mathrm{is}\:\mathrm{non}+\mathrm{periodic} \\ $$$$\Rightarrow\:\mathrm{just}\:\mathrm{calculate}\:\mathrm{it} \\ $$$${a}=\mathrm{1} \\ $$$${b}=\lfloor\frac{\mathrm{1}}{\:\sqrt[{\mathrm{3}}]{\mathrm{2}}−\mathrm{1}}\rfloor=\lfloor\sqrt[{\mathrm{3}}]{\mathrm{4}}+\sqrt[{\mathrm{3}}]{\mathrm{2}}+\mathrm{1}\rfloor=\mathrm{3} \\ $$

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