The function f(x) = 3e^-x represents the exponential decay of a unit of kryptonite in grams per year, where x is years. Using the graph you made, how many years (x) does it take for the kryptonite to be less than 0.055 grams?
In order to answer the question, we have to solve the equation: [tex]3e^{-x}\ \textless \ 0.055,\text{ divide by 3 like this:}\\e^{-x}\ \textless \ \frac{0.055}{3}\\e^{-x}\ \textless \ 0.018,\text{ apply the log function to the two sides of the inequality:}\\-x\ \textless \ \log(0.018)\\-x\ \textless \ -4,\text{ therefore:}\\x\ \textgreater \ 4[/tex]
So it take 4 years in order to the kryptonite to be less than 0.055 grams.
