How do you know a relationship b/w x and y is a function?

i'm really bad at algebra.... *sigh*

apparantly the dictionary meaning for a "function" is:

a cosistent, predictable, relationship between the independant and dependant variable...

but i cant figure out all that mathematical jib-jab gibberish.

4 Answers

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  • 1 decade ago
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    basically, think of a function as a machine:

    take this an an example: f(x) = 2x +3

    see the x in brackets?

    if x = 1, then f(1) = 2(1) + 3 = 5

    if x = 2, then f(2) = 2(2) + 3 = 7

    if x = 3, then f(3) = 2(3) + 3 = 9

    see whats happening? the answer DEPENDS on number inputted in the brackets.

    so therefore, the definition you quoted "a consistent, predictable, relationship between the independant and dependant variable" is true.

  • 1 decade ago

    The people below gave you right answers but if you ask me it is too complicated.

    know this.

    After getting a set of coordinates (x and y) check them all and make sure the x coordinate doesn't repeat itself if so it is not a function, however the y coordinate can repeat itself and that relation can still be a function for example

    (x , y)

    2, 3

    3, 4 Not a function

    4, 3

    2, 5

    this relation is not a function

    because on the x coordinate

    you have a number thatt repeats itself

    and that number is 2.

    NOTE= as long as tha X doesn't repeat itself then that relation is a function.

    (x,y)

    2,3

    4,4

    6,4 this is a function because the x coordinate didn't repeat itself.

    0,3

    I hope this helps you. good luck

  • y(x) = x is a function because for every value of x there is only one value of y.

    i.e. y(x) = 2x

    when x = 2 then y = 4. If you know x then you can find y

  • 1 decade ago

    wen it says f(x)

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