Linear Law - Plotting Linearised Data and Lines of Best Fit

Linear Law - Plotting Linearised Data and Lines of Best Fit

The table below shows experimental values of two variables \(x\) and \(y\) which are connected by an equation of the form \(ax^2 + by = 1\), where \(a\) and \(b\) are constants.

\(x\)\(1\)\(2\)\(3\)\(4\)\(5\)\(6\)
\(y\)\(0.47\)\(0.87\)\(1.53\)\(2.47\)\(3.87\)\(5.14\)

Using a suitable scale, plot the graph of \(y\) against \(x^2\). Use your graph to

  1. determine which value of \(y\) is inaccurate and estimate its correct value,
  2. estimate the value of \(a\) and of \(b\).
  3. By drawing a suitable straight line, find the values of \(x\) and \(y\) which satisfy the following pair of simultaneous equations.
    \(ax^2 + by = 1\)
    \(2x^2 + y = 3\)

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Answer:(i) The value y=3.87 at x=5 is inaccurate; corrected y≈3.7. (ii) a≈-0.380, b≈2.86. (iii) x≈1.11, y≈0.515.

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