A scientist models the activity, AAA MBq, of a radioactive isotope over time, ttt days, using the equation
A=(15t+2)e−0.4t,t≥0 A = (15t + 2)e^{-0.4t}, \quad t \ge 0 A=(15t+2)e−0.4t,t≥0Find, using calculus, the exact value of ttt for which the activity is stationary.
375 exam-style questions on AQA A Level Maths 1.10 G: Differentiation, covering 1.10.1 The derivative and second derivative, 1.10.2 Differentiating standard functions, 1.10.3 Applications of differentiation, 1.10.4 Product, quotient and chain rules (A-level only), 1.10.5 Implicit and parametric differentiation (A-level only), and 1.10.6 Constructing differential equations (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.