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A computer scientist is testing a root-finding algorithm. The scientist tests the algorithm on the equation

x2+x−9=0

The computer attempts to use the iterative formula

xn+1=9−xnxn

with a starting value of x0=2.5 and terminates after the third iteration, x3, has been found.

  1. Find the percentage error between x3 and the true value of the root.

  2. Suggest an alternative iterative formula the computer could use, and evaluate this against the previous formula.


Give the percentage error found in part (a), correct to 2 decimal places.