Linear Law - Predictions from Linearised Models

Linear Law - Predictions from Linearised Models

The table below shows experimental values of \(x\) and \(y\) which are connected by an equation of the form \(y = m^{n+x}\), where \(m\) and \(n\) are constants.

\(x\)\(0.1\)\(0.2\)\(0.3\)\(0.4\)\(0.5\)\(0.6\)
\(y\)\(5.9\)\(6.9\)\(7.2\)\(9.4\)\(11.0\)\(13.1\)
  1. Express \(y = m^{n+x}\) in a form suitable for drawing a straight line graph, stating clearly the variables that are to be plotted.
  2. Using these variables, draw the straight line graph and hence state the correct value of \(y\) that is erroneous.
  3. Use your graph to estimate the value of \(m\) and of \(n\).
  4. Use your graph to estimate the value of \(y\) when \(\lg x = -0.456\).

Solution:

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Answer:(i) Plot \(\lg y\) against \(x\): \(\lg y=x\lg m+n\lg m\). (ii) Replace \(7.2\) by approximately \(8.1\). (iii) \(m\approx5.0,\ n\approx1.0\). (iv) \(y\approx8.8\), using the displayed fitted line.

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