College Algebra
Answer/Discussion to Practice Problems
Tutorial 25: Slope of a Line
Answer/Discussion
to 1a
(2, 5) and (1, 1) 

*Plug in x and y values into slope formula
*Simplify

Make sure that you are careful when one of
your values is negative and you have to subtract it as we did in line 2.
5  (1) is not the same as 5  1 and 2  (1) is not the same as 2 
1.
The slope of the line is 4/3.
Since the slope is negative, the line would fall (left to right). 
Answer/Discussion
to 1b
(7, 1) and (7, 2) 

*Plug in x and y values into slope formula
*Simplify

The slope of the line is undefined.
Since the slope is undefined, the line is vertical. 
Answer/Discussion
to 1c
(1, 7) and (2, 2) 

*Plug in x and y values into slope formula
*Simplify

Make sure that you are careful when one of
your values is negative and you have to subtract it as we did in line 2.
7  (2) is not the same as 7  2 and 1  (2) is not the same as 1  2.
The slope of the line is 3.
Since the slope is positive, the line would rise (left to right). 
Answer/Discussion
to 1d
(1, 5) and (4, 5) 

*Plug in x and y values into slope formula
*Simplify

Make sure that you are careful when one of
your values is negative and you have to subtract it as we did in line 2.
5  (5) is not the same as 5  5 and 1  (4) is not the same as 1
 4.
The slope of the line is 0.
Since the slope is zero, the line is horizontal. 
Last revised on Jan. 16, 2010 by Kim Seward.
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