SOLUTION: Hi, the question i have is that a computer is purchased at end of 1999 for $3000. Scrap value of the computer in 2001 is expected to be $500. Find a linear function that describe

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Question 55055: Hi, the question i have is that a computer is purchased at end of 1999 for $3000. Scrap value of the computer in 2001 is expected to be $500. Find a linear function that describes the value of the computer, if t is the age of the computer in years.
I wouldn't know where to start!! thanks.
Answer by Hook(36) About Me  (Show Source):
You can put this solution on YOUR website!
The problem asks you to find a linear funtion: let's call it f%28t%29.
We know its a line, so it can be of the form f%28t%29=mt%2Bb (That's slope-intercept form there).
What do we know?
We're calling t the age of the computer. In '99, we're at t=0 and the computer is worth $3000; in '01 t=2, the computer is worth $500.
Ok, so we have these two points:
(0,3000)
(2,500)
Let's plug the first point into that slope-intercept form of our line:
3000=m%280%29%2Bb
The m term drops away and we're simply left with
3000+=+b
Great. Now lets plug the second point into our equation (we know b now as well)
500+=+m%282%29+%2B+3000}
If we subtract 3000 from both sides, we get
-2500+=+2m
and divide by 2
-1250+=+m
Throw it all together, we get f%28t%29+=+-1250%2At%2B3000
We can eve graph it:
graph%28300%2C200%2C+-1%2C4%2C-1000%2C4000%2C+-1250%2Ax%2B3000%29