The mass, m m\,m milligrams, of a culture of bacteria is modelled by
m=f(t)m = f(t)m=f(t), where f(t)=20e0.4tf(t) = 20e^{0.4t}f(t)=20e0.4t
and t t\,t is the time in hours after the culture is prepared, for 0≤t≤120 \leq t \leq 120≤t≤12.
Using set notation, state the range of fff. Give the upper limit to three significant figures.
Find an expression for f−1(m)f^{-1}(m)f−1(m), and state what f−1(m)f^{-1}(m)f−1(m) represents in this context.
Explain why this model should not be used to predict the mass of the culture three days after it is prepared.
281 exam-style questions on CCEA A Level Maths 3.1 Algebra and functions (A-level only), covering 3.1.1 Algebra and functions (A-level only), 3.1.2 Algebra and functions (A-level only), 3.1.3 Algebra and functions (A-level only), 3.1.4 Algebra and functions (A-level only), 3.1.5 Algebra and functions (A-level only), 3.1.6 Algebra and functions (A-level only), 3.1.7 Algebra and functions (A-level only), 3.1.8 Algebra and functions (A-level only), 3.1.9 Algebra and functions (A-level only), and 3.1 Algebra and functions (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.