An algebra problem by Jason Chrysoprase

Algebra Level 3

5 a 2 c 4 c 2 e + e 3 5 b 2 d 4 d 2 f + f 3 \sqrt{\dfrac{5a^2c-4c^2e+e^3}{5b^2d-4d^2f+f^3}}

If a b = c d = e f = 64 \dfrac{a}{b} = \dfrac{c}{d} = \dfrac{e}{f} = 64 , find value of the expression above.


The answer is 512.

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1 solution

Jason Chrysoprase
Jul 31, 2016

5 a 2 c 4 c 2 e + e 3 5 b 2 d 4 d 2 f + f 3 = 5 × 6 4 2 × b 2 × 64 × d 4 × 6 4 2 × d 2 × 64 × f + 6 4 3 × f 3 5 b 2 d 4 d 2 f + f 3 = 6 4 3 ( 5 b 2 d 4 d 2 f + f 3 ) 5 b 2 d 4 d 2 f + f 3 = 6 4 3 = ( 2 6 ) 3 = 2 18 = 2 9 = 512 \begin{aligned} \sqrt{\frac{5a^2c-4c^2e+e^3}{5b^2d-4d^2f+f^3}} & = \sqrt{\frac{5 \times 64^2 \times b^2 \times 64 \times d-4 \times 64^2 \times d^2 \times 64 \times f + 64^3 \times f^3}{5b^2d-4d^2f+f^3}} \\ & = \sqrt{\frac{64^3(5b^2d-4d^2f+f^3)}{5b^2d-4d^2f+f^3}} \\ & = \sqrt{64^3} \\ & = \sqrt{(2^6)^3} \\ & = \sqrt{2^{18}} \\ &= \sqrt{2^9} \\ &= 512 \\ \end{aligned}

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