Ain't it cunning?

Algebra Level 3

( x 5 4 ) 3 = ( x 2 x 2 3 ) 4 5 \sqrt{{\left(\sqrt[4]{{x}^{5}}\right)}^{3}} = \sqrt[5]{{\left(\sqrt[3]{{x}^{2x^2}}\right)}^{4}}

Find the positive real value of x x which satisfies the equation above.
Here x 1 x \neq 1


This is one part of the set Fun with exponents


The answer is 1.875.

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1 solution

Ashish Menon
Apr 25, 2016

( x 5 4 ) 3 = ( x 2 x 2 3 ) 4 5 ( ( ( x 5 ) 1 4 ) 3 ) 1 2 = ( ( ( x 2 x 2 ) 1 3 ) 4 ) 1 5 x 15 8 = x 8 x 2 15 Equating the powers : 15 8 = 8 x 2 15 x 2 = 225 8 \begin{aligned} \sqrt{{\left(\sqrt[4]{{x}^{5}}\right)}^{3}} & = \sqrt[5]{{\left(\sqrt[3]{{x}^{2x^2}}\right)}^{4}}\\ {\left({\left({\left(x^{5}\right)}^{\tfrac{1}{4}}\right)}^{3}\right)}^{\frac{1}{2}} & = {\left({\left({\left(x^{2x^2}\right)}^{\tfrac{1}{3}}\right)}^{4}\right)}^{\frac{1}{5}}\\ x^{\tfrac{15}{8}} & = x^{\tfrac{8x^2}{15}}\\ \text{Equating the powers}:-\\ \dfrac{15}{8} & = \dfrac{8x^2}{15}\\ x^2 & = \dfrac{225}{8} \end{aligned}

Positive real value of x = 15 8 = 1.875 \therefore \text{Positive real value of x} = \dfrac{15}{8}\\ = \boxed{1.875}

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