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# Need help!

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The numbers x^3 and y^3 are inversely proportional. If x = 2 when y = 15, what is y if x = 1 and y is positive? Write your answer in simplest radical form.

Thank you.

Mar 24, 2019

#1
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I will answer this again, taking into account that you said radical form.

As a note, you may have copied your question incorrectly as I know a question similar to this one but instead, one of them is x^2 and y^3 or x^3 and y^2. So, if you did miswrite it, please rewrite it and I will solve it correctly. :)

Inversely proportional means that the product stays constant. If x^3y^3 stays constant, then taking the cube root maens xy stays constant, so xy = 2*15 = 30, so when x = 1, y = 30. No radicals needed. :)

Mar 24, 2019
#2
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Hi,

yes I am sorry I did make a mistake when copying the problem it should be "The numbers x^3 and y^2".

Mar 24, 2019
#3
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We have that

y^2  = k /x^3       and we know that

15^2 = k / 2^3

k =  15^2 / 2^3  =   225/8

So....

y^3 = (225/8) / 1^3

y^3 = (225/8)

y = (225/8)^(1/3)  =  ∛225/ 2   Mar 25, 2019