Solving x^(2/3)=4: Logarithms or What?

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To solve the equation x^(2/3) = 4, understanding fractional exponents as radicals is crucial. The denominator indicates the root, while the numerator indicates the power applied to x. The method discussed involves rewriting x^(2/3) as the cube root of x squared and equating it to 4. By taking the square root of 4, which is 2, and then cubing it, the value of x is determined to be 8. The approach used in the discussion confirms that the solution is correct and follows proper mathematical methods.
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:frown: I don't remember how to do this x^(2/3)=4 solve for x Do you use logarithm or something?
 
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I'm going to try my best to explain. Whenever you have a fractional exponent, that is another way of talking about a radical...


The "3" in the denominator of the fraction is what "root" your radical will be:

Ex. square root of 2 = 21/2
cubed root of 2 = 21/3

now, the numerator is what power "X" is going to be:

Ex. square root of 21 = 21/2
cubed root of 22 = 22/3

That should hopefully get you started in the right direction...
 
After reading what you said I did the following.

wrote x^2 with the third root around it and made it equal 4.

I then took the square root of 4 to get rid of the square sign on x

I then cubed the 2 and got 8

After pugging the 8 into x^(2/3) I got 4

Please tell me I got the answer using a proper method and this isn't a cruel coincidence. Thanks by the way for the help!
 
Last edited:
Mozart said:
After reading what you said I did the following.
wrote x^2 with the third root around it and made it equal 4.
I then took the square root of 4 to get rid of the square sign on x
I then cubed the 2 and got 8
After pugging the 8 into x^(2/3) I got 4
Please tell me I got the answer using a proper method and this isn't a cruel coincidence. Thanks by the way for the help!

sounds like you did it right.
 
Thanks.
 
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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