# Given y a x where y is 6 and x is 2, find y when x is 7?

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• y a x where y is 6 and x is 2, find y when x is 7?

I will guess that y a x  .. is y is directly proportional to x

y/x = y/x

6/2 = y/7  <<<  solve for y

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• y a x ?? what does this mean ?

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• 21would be a reasonable answer if you are measuring linearly

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• If you were trying to say y is proportional to x, then the answer is

7*(6/2) = 21.

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like suppose y = x + 4 then y = 6 when x = 2 and hence y = 11 when x = 7

but suppose y = x^2 + 2 then y = 6 when x = 2 and y = 51 when x = 7

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• rule:

assume y ∝ xthat is y = kx , with constant k≠0

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• I'm not sure of your notation (y a x). I believe you are trying to say that y is directly proportional to x:

y ∝ x

Another way to write that is:

y = kx, where k is a constant of proportionality.

We are given one case when y = 6 and x = 2, so plug those in and solve for k:

6 = k * 2

6/2 = k

k = 3

So the final equation is:

y = 3x

That basically says that the value of y is 3 times the value of x.

Now we can easily figure out any x or y, given the other variable. For example, when x = 7

y = 3(7)

y = 21

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