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Can someone provide an example and counter example of a function ?

User Julivico
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2 Answers

3 votes

Answer:

A weekly salary is a function of the hourly pay rate and the number of hours worked

User Sanedroid
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Explanation:

a function is a map assigning values of a result or solution set to values of a set of initial or starting values.

we typically name these starting values x and the solution values f(x) or y (the results "created" out of x).

we often say

y = f(x)

and provide an expression or table to explain the logic of the mapping between x and f(x).

the only rule to be a function and not just a general relationship between these 2 sets :

every value in the set of starting values must have exactly one assigned solution value. not 0, not 2 (or more). one and only one.

but yes, different values of x can have the same assigned solution value. that is not a problem for a function. it just cannot be the other way around. there cannot be different solution values assigned to the same value of x.

so, a typical example of a function is a line.

e.g.

y = f(x) = 5x + 12

for every value of x you could think of (and everything else) there is exactly one result value calculated.

or the score board in a sports event :

athlete 1 : 12 points

athlete 2 : 24 points

athlete 3 : 20 points

athlete 4 : 22 points

...

the athletes are the "x". and their associated points the "f(x)" or "y".

no athlete is listed multiple times with different scores.

a typical example of not being a function is a circle. for almost every value of x inside the circle (that means for almost every point of the horizontal diameter of the circle) there are 2 values of y (that means points on the arc of the circle) : one above and one below the diameter.

or a strange score board like

athlete 1 : 12 points

athlete 2 : 24 points

athlete 3 : 20 points

athlete 2 : 22 points

athlete 4 : 22 points

...

athlete 2 is listed twice with 2 different scores.

so, this is therefore not a function.

User Freddoo
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