Exercise 57 Page 288

We can model the price of sweater using an exponential decay function, since each day the prices are reduced by the same amount, 20 %. y= a(1- 0.2)^t ⇔ y=a(0.8)^t Here, a is the initial price of the sweaters. Let's find the price of the sweater in terms of a on the fifth day.

y=a(0.8)^t

Substitute

t= 5

y=a(0.8)^5

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Simplify right-hand side

CalcPow

Calculate power

y=a(0.32768)

RoundDec

Round to 2 decimal place(s)

y=a(0.33)

We see that on the fifth day the price of the sweater is not equal to zero. The store does not make a 20 % discount on the original price each day.