Part A
The equation is g = -2.5m + 20
The +20 represents us starting with 20 gallons. The -2.5m portion indicates losing 2.5 gallons per minute. So after m minutes, we'll have -2.5m+20 gallons left.
The smallest m can be is m = 0
Let's plug in g = 0 and solve for m to find the largest possible m value
g = -2.5m + 20
-2.5m + 20 = g
-2.5m + 20 = 0
-2.5m = -20
m = (-20)/(-2.5)
m = 8
At the 8 minute mark is when g = 0. So this is when the tub is completely empty. We cannot go beyond this point because g would become negative. So m = 8 is the largest m can get.
This means m is between 0 and 8, including both endpoints.
The domain is [tex]0 \le m \le 8[/tex]
The domain is continuous because the number of minutes is continuous. We cannot have a jump in time from something like m = 1 to m = 2 without values in between. In other words, to go from m = 1 to m = 2, we need to pass by something like m = 1.5
No matter what two values you pick in the interval mentioned, there is always going to be some midpoint and infinitely many other values to deal with.
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Answers:
- Domain: [tex]0 \le m \le 8[/tex]
- The domain is continuous
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Part C
See the graph below. The table is included as well.
To generate the table, we select values of m from the domain found earlier. I'm using whole numbers for m, but you can use any real number you want from that interval.
Let's say we picked m = 2
That would mean,
g = -2.5m + 20
g = -2.5*2 + 20
g = -5 + 20
g = 15
So at the 2 minute mark, the tub will have 15 gallons left. That means we'll have a row with m = 2 and g = 15 pair up together. The rest of the table is generated in a similar fashion.
Once the table is set up, you plot all of the points and draw a line through them to complete the graph.
Because we're dealing with a linear function, we only need 2 points at minimum to graph it. However, you can generate as many points as you want. It could be good practice.
Side note: Stuff to the left of m = 0 and stuff to the right of m = 8 is not graphed, as these portions are not in the domain.
