Posted by **Milia** on Sunday, June 5, 2011 at 5:35am.

How would you tell if an equation is a funtion or not. I know that it has to have only one y-value for every x...but how do you identify this in an equation (rather than a graph)

ie. y=1/2x-7 (how do i tell if this is a funtion or not)?

Any help would be much appreciated :)

- Math -
**Andy**, Sunday, June 5, 2011 at 6:28am
when dealing with linear functions, the general formula is y= mx + c..where m is the gradient and c is the y-intercept. To find the value of x simply make y = to zero.hence the equation(y=1/2-7) is a linear function because if substituted in the general formula,1/2 would be the gradient(since it is the value/coefficient of x),, c=-7 and x=-1.

- Math -
**drwls**, Sunday, June 5, 2011 at 6:28am
Please use parentheses where needed for clarity. I don't know if that is

1/(2x-7) or (x/2) -7 or (1/2x) -7

In each case, y is clearly a function of x because there is one and only one y for each x. (Except possibly where a denominator vanishes)

- Math -
**Milia**, Sunday, June 5, 2011 at 6:40am
thanks :)

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