A bacteria culture starts with 80 cells and grows by 25% per hour. Which function models the count after $x$ hours?
A$f(x) = 80(0.25)^x$
B$f(x) = 80(1.025)^x$
C$f(x) = 80(1.25)^x$
D$f(x) = 80 + 25x$
Answer & Solution
Correct answer: C. $f(x) = 80(1.25)^x$
Growth rate 25% means $b = 1 + 0.25 = 1.25$. So $f(x) = 80(1.25)^x$. Option A models 75% decay; option B is 2.5% growth; option D is linear growth, not exponential.
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