Project Math Access DVD 03 - Algebra - Part 10
Transcript Start
Audio Description: Part ten; solving equations using graphing; example four.
TEACHER: We are going to skip ahead to problem number 11. because it has a fraction for slope already built in.
BRANDON: Haaa. Graph Y equals negative one-fifth X minus 5.
TEACHER: Good.
BRANDON: Now, now this is one of the real easy kinds of problems
TEACHER: Why?
BRANDON: Because it gives you the fraction, it gives you the rise over run. So, remember, always start from the origin, that is very important. Start from the origin, always, everytime.
TEACHER: Okay. Go ahead.
BRANDON: So, starting from the origin we have a negative one-fifth, Now you want to be careful, even though this is rise over run with a negative, you go down.
TEACHER: Okay. Do we start with the slope, though when we're graphing a line?
BRANDON: We need to start with the Y intercept so negative 5 on the Y we go... down 5.
1, 2, 3, 4, 5. Plot a point. Whoa. Kind of crooked here.
Audio Description: Brandon places a point at -5, Y.
BRANDON: That's better.
TEACHER: And then your slope was... ?
BRANDON: Negative one-fifth.
TEACHER: Right.
BRANDON: So now I want to go down 1, Don't go up 1, because that would be positive.
TEACHER: Well, you could go up, but then you would have to go what direction?
BRANDON: You'd have to go left 5, and that would be hard. So, we want to go down 1, and to the right 5. 4, 5.
TEACHER: And why do we go to the right?
BRANDON: Because that last number is still positive.
TEACHER: So positive means go to the right, and negative means go to the left.
BRANDON: Right, negative means go to the left. And positive means go up, and negative means go down. And then we want another one, so...
BRANDON: negative 1... Right?
TEACHER: Uh huh
BRANDON: And then negative 5? Positive 5.
TEACHER: Okay.
BRANDON: So, 1, 2, 3,4, 5.
TEACHER: Alright.
Audio Description: Brandon places a third point on the graph.
BRANDON: Don't move point, please.
Audio Description: Brandon grabs a Wikki Stix.
BRANDON: So, I'm going to take our Wikki Stix (chuckles)
TEACHER: What do you do with that Wikki Stix?
BRANDON: We pull it taut
TEACHER: Pull it taut. Lay it across the...
BRANDON: Points.
TEACHER: The points.
TEACHER: But as you're laying it down it's getting all wiggly. So what might be good here?
BRANDON: (groaning) The ruler.
TEACHER: The ruler.
TEACHER: I could give you my pencil. That would work. You could lay that across the points and then you'd have a guide. of course, you're fingers are in the way, so that wouldn't work.
Audio Description: The Wikki Stix is curved, missing the middle point.
TEACHER: Did you go through all 3 points?
BRANDON: Well, that's what I'm not sure about.
TEACHER: Yea, me either.
BRANDON: Brandon's hand searches the first quadrant.
TEACHER: Are there points way up there? Start with your Y intercept as the first point. The Y intercept was negative 5, right?
BRANDON: Yeah.
TEACHER: Okay.
TEACHER: And then your slope was negative 1... 5. So what direction do you think you need to go?
BRANDON: Negative 1, is down 1, and then to the right 5.
TEACHER: There's your point. Don't take it off the other one.
Audio Description: Brandon adjusts the Wikki Stix.
TEACHER: Okay, how about the next, the third point?
Audio Description: The Wikki Stix is slightly bent between the second and third points.
TEACHER: That's a pretty squiggly |ine YOU got going there.
BRANDON: (unintelligible)
TEACHER: Well, find your second point. Use your slope to find it. Negative 1, 5.
Audio Description: Brandon moves his hand to the origin.
TEACHER: Start at negative 5 to find your first point.
Audio Description: Brandon moves his hand down along the Y axis.
TEACHER: And then you have negative 1, 5 for the second point.
BRANDON: Oops.
TEACHER: All you have to do is go down 1 line and slide over to the right until you find the next point. You already plotted it. It's stuck there.
BRANDON: Right.
TEACHER: It's not moving. You've got it pretty well anchored. So you want to find your third point. So go down one and slide over... Find the next one... to the right.
BRANDON: It's there.
TEACHER: Now feel your line. Does it feel straight.
BRANDON: Yeah, that's the thing...
TEACHER: Run your finger along the line and see if it's straight.
BRANDON: Uhhh... well...
TEACHER: Here, let me lay my pencil on here so you can... lift up
BRANDON: Wait a minute.
Audio Description: The line is still bent between points two and three. The teacher puts a pencil on the line.
TEACHER: This line has a disease. There's a lump in the middle
BRANDON: (laughs) Oh, no.
TEACHER: Alright, I'm laying my pencil there. It's intersecting the 3 points. Where is the line in relation to my pencil? You feel that lump right there? Let's cure it.
BRANDON: It's sick.
TEACHER: It's sick.
BRANDON: (jokingly) Ohhhh nooooo.
Doctor, doctor. We have a sick pencil!
Audio Description: The line is now straight.
TEACHER: Alright, let's see. That looks a lot better. Now my pencil's stuck to it. That's a lot straighter. So, using something stiff to line it up would help. Rulers preferred. Pencils roll around too much.
BRANDON: That they do.
TEACHER: Alright, good job.