Question

I need to make tables of values for both horizontal and vertical stretching, but I wasn't in class and missed the lesson. I don't really understand how to get the values; at first I figured you'd get the value of y by just pluging in whatever value of x you're given to y=f(x), but this doesn't seem to work. My book shows completely different answers, but doesn't explain how to get them.

I'm given a table of values for y=f(x) with (-4,0), (-2,4), (0,-4), (2,4), (4,0). Then, I am to find the y values for y=2f(x) and for y=1/2f(x) and for y=f(2x) and y=F(1/2x).

I'm guessing that if there's an actual number inside the parenthesis, it's a horizontal stretch, but I still can't figure out how to actually do it.

Please help me.