SOLUTION: The depreciated value V of a machine is a linear function of time t in years. A machine that is purchased for $100000 today will be worth approximately $67681 in 3 years. Write the

Algebra ->  Linear-equations -> SOLUTION: The depreciated value V of a machine is a linear function of time t in years. A machine that is purchased for $100000 today will be worth approximately $67681 in 3 years. Write the      Log On


   



Question 1087082: The depreciated value V of a machine is a linear function of time t in years. A machine that is purchased for $100000 today will be worth approximately $67681 in 3 years. Write the linear function V(t) that represents the value of the machine at a given time t.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
The value today is V = 100000 dollars when the time is t = 0, which is the starting time value.
The value in 3 years, when t = 3, is V = 67681 dollars

So we have two ordered pairs (0,100000) and (3,67681). I'm going to treat t as x, and treat V as y. So each ordered pair goes from the form (t,V) to (x,y). Using the (x,y) form we can use the slope formula

First point = (x1,y1) = (0,100000)
Second point = (x2,y2) = (3,67681)
m+=+%28y%5B2%5D+-+y%5B1%5D%29%2F%28x%5B2%5D+-+x%5B1%5D%29
m+=+%2867681+-+100000%29%2F%283+-+0%29
m+=+%28-32319%29%2F%283%29
m+=+-10773

So the slope is m+=+-10773 meaning that each year the value drops by $10,773

The y intercept is b+=+100000 because this is the starting value (at t = 0)

So we go from y+=+mx%2Bb to y+=+-10773x%2B100000

The last thing to do is replace x with t and replace y with V(t) to get V%28t%29+=+-10773t%2B100000

Therefore the value function is V%28t%29+=+-10773t%2B100000

-------------------------------------------------

Let's check the function. Plug t = 0 into the function to get
V%28t%29+=+-10773t%2B100000
V%280%29+=+-10773%2A0%2B100000
V%280%29+=+0%2B100000
V%280%29+=+100000
So that matches with the fact the initial value is $100,000

Now plug in t = 3
V%28t%29+=+-10773t%2B100000
V%283%29+=+-10773%2A3%2B100000
V%283%29+=+-32319%2B100000
V%283%29+=+67681
Which matches with the value after 3 years. So the answer is confirmed