Question about changing roots to powers

e.spyck

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Nov 2, 2020
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Amateur here..

I am trying to change this fraction to a number with powers. According to the book, solution should be [7][4/5]. I always arrive at [7][/3/5]. What am I doing wrong?
Thanks for your help!
 

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It seems that the question is asking you to show the following...

775=745 \frac{7}{\sqrt[5]{7}} = 7^{\frac{4}{5}}

But on your first 2 lines you imply...

775=775 \frac{7}{\sqrt[5]{7}}=\sqrt[5]{\frac{\color{red}7\color{black}}{7}} but this isn't correct.


Think about the numerator only, what value of "x" would satisfy...

7=7x5 7=\sqrt[5]{7^x}

EDIT: When you find x, then the following progression would be correct...

775=7x575=7x75 \frac{7}{\sqrt[5]{7}}= \frac{\sqrt[5]{7^x}}{\sqrt[5]{7}} = \sqrt[5]{\frac{7^x}{7}}... and continue
 
Last edited:
I would do it the other way around:
775=7171/5=711/5=75/51/5\displaystyle \frac{7}{\sqrt[5]{7}}= \frac{7^1}{7^{1/5}}= 7^{1-1/5}= 7^{5/5- 1/5}.

an=a1/n\displaystyle \sqrt[n]{a}= a^{1/n} and 1an=an\displaystyle \frac{1}{a^n}= a^{-n}.
 
Or you could it do your way but correctly

[MATH]\dfrac{7}{\sqrt[5]{7}} = \dfrac{\sqrt[5]{7^5}}{\sqrt[5]{7}} =[/MATH]
[MATH]\sqrt[5]{\dfrac{7^5}{7}} = \sqrt[5]{7^4} = 7^{4/5}.[/MATH]
 
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