Activities

Numerical methods of solving equations - one point iterative methods



Consider the quadratic equation .
There are two real solutions as the graph of  intersects the x-axis in two places.
The equation can be rearranged in the form .

Any such rearrangement can be used as an iterative process  to produce a sequence of numbers.

Different starting numbers can be tried to see whether the sequence converges to a limit. Any limit that exists is a solution of the equation.

Rearrangement 1

Suppose the starting number is 4.
The screen shots show that the sequence converges to the limit 2.0697 (accurate to 4 decimal places). This is one of the two solutions of the equation .

Try other starting values. Can you find the other solution (approximately -1)?

Having difficulties? Try different rearrangements. (See 2 or 3.)


How can we tell whether an iterative process  will converge to a particular solution?

It depends on:

See the activity on sequence graphs and web plots.