Question 148068
A "function" can provide only a "single" solution for any given input.
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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) 
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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.
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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.
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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.
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THEREFORE, the solution is set 3:
 (2,3),(-4,5),(-2,7),(7,7)