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It's about variation.

Thanks!

2007-01-10 23:52:22 · 7 answers · asked by Anonymous in Science & Mathematics Mathematics

7 answers

One solution is y = x^(1/3) - 1

Another is y = (2/3)* x^(1/3)

2007-01-10 23:56:07 · answer #1 · answered by Jerry P 6 · 0 0

As the cube root of 27 is 3 , I assume that the answer is the cube root minus 1

2007-01-10 23:58:13 · answer #2 · answered by Anonymous · 0 0

y varies directly as x^(1/3) means that
y = k * x^(1/3) for some constant k.

Plugging in x = 27 and y = 2 gives :
2 = k * 27^(1/3)
2 = k * 3
k = 2/3

The equation is therefore : y = (2/3) * x^(1/3)

2007-01-11 00:02:10 · answer #3 · answered by falzoon 7 · 0 0

You only have one equation so you can't have a unique solution

The cuberoot of x is 3 but you can perform a whole variety of function to make it 2

Subtract 1
Multiply by 2/3
Divide by 3 and add 1

y = [x^(1/3)] - 1
y = 2/3[x^(1/3)]
y = [x^(1/3)]/3 + 1

Are all valid

edit: Since it is variation the second one is best, with k = 2/3

2007-01-11 00:09:57 · answer #4 · answered by Tom :: Athier than Thou 6 · 0 0

y = k(cube root of x)
cube root of 21 is 3
2 = k3
the constant is 3/2 = 1.5

2007-01-10 23:58:36 · answer #5 · answered by Mr Asker Knowmore 2 · 0 0

The equations are as follows:
y = k * qrt(x), or
y^3 = k1 * x ..........1)
Substitute your numbers in 1) above to obtain k1
2*2*2 = k1 * 27
or k1 = 8/27
Now rewrite 1) with value for k1
y^3 = 8/27 * x
or y = 2/3 * qrt (x)

2007-01-11 00:03:38 · answer #6 · answered by Paleologus 3 · 0 0

Do you mean find an equation ?
If yes , one of the solutions is :
x^(1/3)-1= y;
But because you ask "direct variation" it is rather a term used for linear equations :
y= x^(1/3)*(2/3)

2007-01-10 23:57:08 · answer #7 · answered by Luis U 2 · 0 0

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