Question 85100
The undefined slope is the clue.  It tells you that the graph is a vertical line. Why so?
Because the slope will always have a real value as long as there is a change in x. Recall
that the slope is defined as:
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{{{Slope = (rise)/(run) = (vertical change)/(horizontal change)}}}
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But if the run (horizontal change or change in x) is zero, the slope is undefined 
because in algebra division by zero is not allowed.
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Therefore, we know the horizontal change in the graph is zero.  So the graph shows that no
matter what the value of y is, x always has to be the same because it cannot change.
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Now the question is where would the vertical line be.  Well, since it has to go up through
the y value of 1, it must have the x value that corresponds to the y value of 1.  The problem
tells you that the x corresponding x value is -2/3. 
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So the graph you are looking for is a vertical line that goes through -2/3 on the x axis
and therefore, it goes through 1 in the y direction as well as lots of other y values in
both the positive and negative direction. The equation for this line is x = -2/3.
There is no y in the equation at all because y can be any value, but x always has to
be -2/3 so that the line will go up through the value of y = 1.
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Hope this helps you to understand the problem and its answer a little better.
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