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Example Questions
Example Question #1 : Determine If A Relation Is A Function
Which of the following expressions is not a function?
Recall that an expression is only a function if it passes the vertical line test. Test this by graphing each function and looking for one which fails the vertical line test. (The vertical line test consists of drawing a vertical line through the graph of an expression. If the vertical line crosses the graph of the expression more than once, the expression is not a function.)
Functions can only have one y value for every x value. The only choice that reflects this is:
Example Question #1 : Determine If A Relation Is A Function
Suppose we have the relation on the set of real numbers
whenever
. Which of the following is true.
The relation is a function because every relation is a function, since that's how relations are defined.
The relation is a function because holds and
also holds.
The relation is not a function because and
both hold.
The relation is a function because for every , there is only one
such that
holds.
The relation is not a function because holds but
does not.
The relation is not a function because and
both hold.
The relation is not a function because and
hold. If it were a function,
would hold only for one
. But we know it holds for
because
and
. Thus, the relation
on the set of real numbers
is not a function.
Example Question #1 : Determine If A Relation Is A Function
Consider a family consisting of a two parents, Juan and Oksana, and their daughters Adriana and Laksmi. A relation is true whenever
is the child of
. Which of the following is not true?
The relation is not a function because (Laksmi,Juan) and (Laksmi,Oksana) both hold.
(Laksmi,Adriana) does not hold because Adriana is not Laksmi's child.
Even if the two parents had only one daughter, the relation would not be a function.
If the two parents had only one daughter, the relation would be a function.
(Adriana,Laksmi) does not hold because Laksmi is not Adriana's child and is a boy.
Even if the two parents had only one daughter, the relation would not be a function.
The statement
"Even if the two parents had only one daughter, the relation would not be a function."
is not true because if they had only one daughter, say Adriana, then the only relations that would exist would be (Juan, Adriana) and (Oksana,Adriana), which defines a function.
Example Question #1 : Determine If A Relation Is A Function
Which of the following relations is not a function?
The definition of a function requires that for each input (i.e. each value of ), there is only one output (i.e. one value of
). For
, each value of
corresponds to two values of
(for example, when
, both
and
are correct solutions). Therefore, this relation cannot be a function.
Example Question #2 : Determine If A Relation Is A Function
Given the set of ordered pairs, determine if the relation is a function
No
Yes
Cannot be determined
No
A relation is a function if no single x-value corresponds to more than one y-value.
Because the mapping from goes to
and
the relation is NOT a function.
Example Question #1 : Determine If A Relation Is A Function
What equation is perpendicular to and passes throgh
?
First find the reciprocal of the slope of the given function.
The perpendicular function is:
Now we must find the constant, , by using the given point that the perpendicular crosses.
solve for :
Example Question #1 : Determine If A Relation Is A Function
Is the following relation of ordered pairs a function?
Yes
Cannot be determined
No
Yes
A set of ordered pairs is a function if it passes the vertical line test.
Because there are no more than one corresponding value for any given
value, the relation of ordered pairs IS a function.
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