If you imagine that it loses 15% each year then after no time it is at full value, then after one year it is t(1-0.15) and after two t(1-.15)(1-.15) and so after n years we get:

T(x) is the value at any given value of n

T(0) is the value at x=0 (ie original value)

x is the factor of depreciation (x>0 for inflation)

n = number, in this case years.

plug in your numbers,

T(0) = 245,000

x = -0.15

n = 4

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I'll try and explain a bit here:

the (1+x)^n is because it is gaining/losing a constant amount each year over n years. If was different amounts each time you'd get (1+a)(1+b)(1+c)... and there would be n sets of brackets. However, because it's the same we get (1+x)(1+x)(1+x) n times which is (1+x)^n.

At n=0 for example we get and since a^0 = 1 we get T(x)=T(0) which is what we'd expect from the definitions. As n increase the importance of the (1+x)^n term will increase and it will rapidly exceed T(0), while it will never reach 0 it will become worthless as it'd drop below a cent.