Hi, this is Maria's daughter. I was doing my Prentice Hall Algebra 1 book, and I found some kind of mistake or or misunderstanding, I am not sure what. In part three of Lesson 74 it says to move two units down and one to the right, which is the point (2,1). Then It says that the point is (1,1) which it is certainly not. They even graphed it like that, so I can not tell if it is a misprint or if I just don't understand their explanation. The concept itself doesn't seem too hard, but this example is confusing me. Could I please have some help? Thank you!!
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Hello!
It looks like you are asking about Example 5 on p. 325. The example is showing how to graph a line using slope intercept form of an equation, y = mx + b, where m is the slope, and b is the yintercept.
Step 1: Identify the yintercept from the given equation y = 2x + 3
The yintercept is 3. The coordinates for this point are (0,3) The point is on the yaxis, that is why the x coordinate is zero. (This is another way to describe the yintercept.)
Graph the yintercept (0,3). This point is the starting place for step 2.
Step 2: Use the slope to determine another point on the line.
Identify the slope. The coefficient of x is 2, so the slope is 2, which can also be written as 2/1 . The numerator, 2, is the "rise" (vertical travel). The denominator, 1, is the "run" (horizontal travel)
The negative "rise" means to go down 2. The positive run means to go to the right 1 space.
From your starting point (0,3), move down 2 spaces, then right 1 space. This takes to you the point (1,1) Graph that point.
Step 3: Use a straightedge to connect the 2 points (step 1 and step 2). This is the graph of the line described by the given equation.
Let me add some general notes about graphing using slope, using a different slope for another example:
Ex 1: For a slope of 4/7, the rise is 4 (up 4) and the run is 7 (to the right 7). This line slopes up and to the right.
Ex 2: For a slope of 4/7, the rise is 4 (down 4) and the run is 7 (right 7). This line slopes down and to the right.
Ex 3: You could also graph this slope (4/7) as 4/(7), which would give a rise of 4 (up 4) and the run is 7 (to the left 7, since left is the negative direction in the horizontal)
Examples 2 and 3 would give you the same line (both slope down and to the right). Use whichever is more convenient for the location on the particular graph.
Please reply if you still have questions, and I will explain further.Cindy Davis
Science and Math teacher at Highlands Latin School  Indianapolis
ds25 college graduate: independent young adult
ds24 college graduate: 2nd year med school
dd22 college senior: Nursing
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