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a-3-1-5-the-set-of-possible-values-of-a-a-b-3-e-a-3-




Question Number 127305 by MathSh last updated on 28/Dec/20
(a−3)^(−(1/5))   the set of possible values of a  a)(−∞;+∞)  b)(3;+∞)  e)a≠3
$$\left({a}−\mathrm{3}\right)^{−\frac{\mathrm{1}}{\mathrm{5}}} \\ $$$${the}\:{set}\:{of}\:{possible}\:{values}\:{of}\:{a} \\ $$$$\left.{a}\right)\left(−\infty;+\infty\right) \\ $$$$\left.{b}\right)\left(\mathrm{3};+\infty\right) \\ $$$$\left.{e}\right){a}\neq\mathrm{3} \\ $$
Answered by MJS_new last updated on 28/Dec/20
depending on the definition we use...  b=(1/( ((a−3))^(1/5) ))  (1) a∈R∧b∈R; (x)^(1/5) =sign x ((∣x∣))^(1/5)  (i.e. ((−32))^(1/5) =−2  ⇒ a≠3 ⇒ a∈R\{3}  (2) a∈C∧b∈C; (x)^(1/5) =∣x∣e^(i((arg x)/5))   ⇒ a≠3 ⇒ a∈C\{3}
$$\mathrm{depending}\:\mathrm{on}\:\mathrm{the}\:\mathrm{definition}\:\mathrm{we}\:\mathrm{use}… \\ $$$${b}=\frac{\mathrm{1}}{\:\sqrt[{\mathrm{5}}]{{a}−\mathrm{3}}} \\ $$$$\left(\mathrm{1}\right)\:{a}\in\mathbb{R}\wedge{b}\in\mathbb{R};\:\sqrt[{\mathrm{5}}]{{x}}=\mathrm{sign}\:{x}\:\sqrt[{\mathrm{5}}]{\mid{x}\mid}\:\left(\mathrm{i}.\mathrm{e}.\:\sqrt[{\mathrm{5}}]{−\mathrm{32}}=−\mathrm{2}\right. \\ $$$$\Rightarrow\:{a}\neq\mathrm{3}\:\Rightarrow\:{a}\in\mathbb{R}\backslash\left\{\mathrm{3}\right\} \\ $$$$\left(\mathrm{2}\right)\:{a}\in\mathbb{C}\wedge{b}\in\mathbb{C};\:\sqrt[{\mathrm{5}}]{{x}}=\mid{x}\mid\mathrm{e}^{\mathrm{i}\frac{\mathrm{arg}\:{x}}{\mathrm{5}}} \\ $$$$\Rightarrow\:{a}\neq\mathrm{3}\:\Rightarrow\:{a}\in\mathbb{C}\backslash\left\{\mathrm{3}\right\} \\ $$
Commented by MathSh last updated on 28/Dec/20
Thanks sir
$${Thanks}\:{sir} \\ $$

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