Initial Amount: 8 Rate of Decay: 15 % Value of the Function when t=5: ≈ 4.9
Practice makes perfect
Let's start by recalling the general formulas for exponential growth and exponential decay functions.
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Exponential Growth & Exponential Decay [0.8em]
y=a(1+r)^t & y=a(1-r)^t
In both cases, a>0 is the initial amount and r>0 is the rate of growth or decay written in decimal form. Moreover, for exponential decay, r is less than 1. Let's consider the given function.
y= 8(1- 0.15)^t
Our function represents exponential decay, with an initial amount a= 8 and a rate of decay r= 0.15. To rewrite the rate of decay as a percent, we move the decimal point 2 places to the right.
r=0.15 ⇔ r=15 %
Finally, to evaluate the function when t=3, we will substitute 3 for t in the given formula.
