SOLUTION: What is the equation of the line which: a) passes through the point (2, -7) and is parallel to y = 2; and b) passes through the point (-1, 2), and is parallel to the line x = 1

The lines whose equations are y = 2 and x = 1, are special lines,
whose form is not recognizable as y = mx+b, because each contains
only one letter variable.

Actually the first kind y = 2 can be placed in the form y = mx+b,
because the slope is 0 and therefore it can be written y = 0x+2.
y = 2 represents a horizontal line with y-intercept (0,2). It
has no x-intercept.

Here it the graph of y = 2:




The second kind x = 1 cannot be written in the form y = mx+b at
all.  That's because its slope is undefined.  It is a vertical 
line which is so steep that there is no possible number large 
enough to indicate how steep a vertical line is.  x = 1 represents 
a vertical line with x-intercept (1,0).  It has no y-intercept.

Here is the graph of x = 1:

 

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You want a line that:

So here is what you want:

 

The green line is also a special lines, just like the line it is
parallel to, y = 2, and its form is also not recognizable as 
y = mx+b, because it will also contains only one letter variable x.
 
Answer: The green line's equation is y = -7

And y = -7 can be also placed in the form y = mx+b,
because the slope is 0 and therefore it can be written y = 0x-7.
y = -7 represents a horizontal line with y-intercept (0,-7). It
has no x-intercept.  Notice that it did not matter in this case
that the x-coordinate of the point was 2.  It could have been any
other number and the answer would have still been y = -7.

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You want a line in this part that:

So here is what you want in this part:

 

The green line is also a special line, just like the line it is
parallel to, x = 1, and its form is also not recognizable as 
y = mx+b, because it will also contains only one letter variable x.
 
Answer: The green line's equation is x = -1

This green line x = -1 also cannot be written in the form y = mx+b.
That's because its slope is undefined.  x = -1 represents 
a vertical line with x-intercept (-1,0).  It has no y-intercept. 
Notice that it did not matter in this case that the y-coordinate of 
the point was 2.  It could have been any other number and the answer 
would have still been x = -1.

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Edwin