Answer: Choice (b)
{ (1, 3), (3, 1), (4, 3) }
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Work Shown:
The notation "g o f" means g(f(x)). We have f(x) as the inner function that is computed first.
f(x) = { (1,2), (3,5), (4,1) }
The x coordinates of each point are: 1, 3, 4
The y coordinates are: 2, 5, 1
So the input x = 1 goes to y = 2 as the output. That output becomes the input of the g(x) function. Using x = 2 as the input for g, we see that 3 is the output. Check out the diagram below to see how each input goes into f, then goes into g to ultimately determine the x,y pairs. So far we've shown that x = 1 ultimately leads to y = 3.
Let's do another input: if x = 3 is plugged into f(x), then the output is 5 because of the point (3,5). Then x = 5 is plugged into g(x) to get x = 5 lead to y = 1. Ultimately x = 3 leads to y = 1 giving us (3,1) as another point.
Lastly, if x = 4 is plugged into f we get y = 1 as an output, which in turn is plugged into g to get 3 as the final output. The point (4,3) is the last ordered pair.
Again there's a lot to keep track of, so it helps to have a diagram as shown below.