Project - would you please check my answers?

I am working on a project and my linear equation came out to be:
y = 1502.9x - 2847386

This project is about waste and recycling so the equation came from a table that gave a few years and the tons of waste in each of those years.

1) We have to state the slope, so I am saying that the slope is 1502.9 which means that on average there are 1502.9 tons of waste each year. Is this correct?
2) Does the equation have a y-intercept? I am saying that my y-intercept is (0, -2857386).
The question asks what does this mean in terms of the context of the problem.
I am thinking that since our years begin in 1990, it means that that is how much is already present in the landfill? But I'm not entirely sure because I don't understand the negative sign -- please help!

3) Does your equation have an x-intercept? If so, solve to find the x-intercept. I'm really unclear about this one because to me it would seem there would not be an x-intercept since this would be the beginning of time, or, you can't have no trash.

4 answers

#1 ok
#2 the y-intercept is negative. If the records started in 1990, then that is just a back-projection on the slope of the line. Not really much meaning in this context.
#3 the x-intercept is where y=0 (x=1894). That could be when records started, but it is more likely that they started keeping records sometime after that year, like 1990. The line is just a best-fit for the records on hand. It is very likely that before 1990 the rate of growth was much slower, causing the graph to flatten out to the left.
So then if I solved my equation, I would get something like x = 1901, so would I say then that I DID have an x intercept?
every sloping line has an x- and a y-intercept!
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