Depreciation The declining balance method is an accounting method in which the amount of depreciation taken each year is a fixed percentage of the present value of the item. If $y$ is the value of the item in a given year, the depreciation taken is ay for some depreciation rate $a$ with $0<a<1$ and the new value is $(1-a) y$
(a) If the initial value of the item is $y_{0}$, show that the value after $n$ years of depreciation is $(1-a)^{n} y_{0}$
(b) At the end of $T$ years, the item has a salvage value of $s$ dollars. The taxpayer wishes to choose a depreciation rate such that the value of the item after $T$ years will equal the salvage value (see the figure). Show that $a=1-\sqrt{s / y_{0}}$
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