The population of a specific bacteria colony (NNN) recorded h h\,h hours after an experiment began is shown in the table below.
| hhh | 1 | 2 | 4 | 7 | 10 | 12 |
| NNN | 190 | 290 | 660 | 2300 | 7900 | 18000 |
The data is coded using the changes of variable x=hx = hx=h and y=log10Ny = \log_{10} Ny=log10N.
The regression line of y y\,y on x x\,x is found to be y=2.10+0.18xy = 2.10 + 0.18xy=2.10+0.18x.
Given that the data can be modelled by an equation in the form N=abhN = ab^hN=abh where a a\,a and b b\,b are constants, find the values of a a\,a and b b\,b to 3 significant figures.
Give an interpretation of the constant a a\,a in this equation.
Explain why this model might not be reliable for predicting the population after 1 week.
104 exam-style questions on OCR (MEI) A Level Maths 1.8 Exponentials and Logarithms, covering 1.8.1 The function y = a^x, 1.8.2 Convert between index and logarithmic form, 1.8.3 Logarithm as inverse of exponential, 1.8.4 Laws of logarithms, 1.8.5 Values of log_a a and log_a 1, 1.8.6 Solve equations of the form a^x = b, 1.8.7 Reduce y = ax^n and y = ab^x to linear form, 1.8.8 The function y = e^x, 1.8.9 Gradient of e^kx (A-level only), 1.8.10 The function y = ln x, and 1.8.11 Exponential growth and decay. Each one has a worked solution and a mark scheme showing where the marks go.