Question

Look at the sceenshot-- help??

Answer 1

The answer is: 3.
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In the table, the relation (x, y) is not a function is the "missing value" of "x" is: 3.
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Explanation: We are given that the ordered pair: "(3,10)" exists.  In other words, when x = 3, y =10. 
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The "missing value" refers to the "empty box" in the table shown (in the attached screenshot).  The "empty box" shows a "y-coordinate" of "20"; but a "missing" corresponding "x-coordinate".
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The problem asks: 
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In the table, the relation (x, y) is not a function is the "missing value" of "x" is: ____?
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The answer is: 3.
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We know the answer is "3"; because we know that "3" already has 1 (one) corresponding y-coordinate.

By definition, a "function" cannot have ANY "x-coordinates" that have more than one "corresponding y-coordinate".   As such:
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In the table, the relation (x, y) is not a function is the "missing value" of "x" is:
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3.
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Additional information:
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When examining an equation on an actual graph, we can use what is called the "vertical line test".  That is, one can take a pencil and vertically go through the "y-axis", or even examine it visually, to see if there are any "x-values" that have more than one corresponding "y-coordinate".
   If no, then it "passes" the "vertical line test" and is a "function".  
If not, then it does NOT pass the "vertical line test" and is NOT a function.
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