Questions on Algebra: Absolute value answered by real tutors!

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Question 148068: Which set of ordered pairs is a function?
(2,3),(-4,5),(2,7),(7,-2)
(2,3),(-4,5),(-2,7),(-4,-2)
(2,3),(-4,5),(-2,7),(7,7)
(2,3),(-4,5),(2,-7),(7,-2)
: Which set of ordered pairs is a function?
(2,3),(-4,5),(2,7),(7,-2)
(2,3),(-4,5),(-2,7),(-4,-2)
(2,3),(-4,5),(-2,7),(7,7)
(2,3),(-4,5),(2,-7),(7,-2)

Answer by nerdybill(1128) About Me  (Show Source):
You can put this solution on YOUR website!
A "function" can provide only a "single" solution for any given input.
.
The sets provided are in (x,y) pairs:
(2,3),(-4,5),(2,7),(7,-2)
(2,3),(-4,5),(-2,7),(-4,-2)
(2,3),(-4,5),(-2,7),(7,7)
(2,3),(-4,5),(2,-7),(7,-2)
.
Looking at the first set:
(2,3),(-4,5),(2,7),(7,-2)
Notice that if 'x' is equal to 2, there are TWO solutions:
(2,3),(2,7)
So, this can't be a function.
.
Looking at the second set:
(2,3),(-4,5),(-2,7),(-4,-2)
Notice that if 'x' is equal to -4, there are TWO solutions:
(-4,5),(-4,-2)
So, this can't be a function.
.
Looking at the fourth set:
(2,3),(-4,5),(2,-7),(7,-2)
Notice that if 'x' is equal to 2, there are TWO solutions:
(2,3),(2,-7)
So, this can't be a function.
.
THEREFORE, the solution is set 3:
(2,3),(-4,5),(-2,7),(7,7)