TASK: Use bisection to find a zero of the function f(x)=x^3-2x-5.
COMMENT: Although this function is a cubic polynomial, which could have three solutions to the problem, it will actually only have one (real) solution.
INSTRUCTIONS:
        Copy the function "bisection3.m" from the homework directory.
        Write a function wallis.m that evaluates the function whose zero
        we are seeking.
        Write a script which calls bisection3 to seek a zero of the
        wallis function.  Your search should begin in the interval [0,3].
        Then print 
        * the solution x, 
        * the value of wallis(x), 
        * the width of the interval (b-a) (this should be small now!)
 
        display the function and your estimated solution:
        xlist = 101 points in [0,3]
        ylist = wallis ( xlist );
        plot ( xlist, ylist, 
               xlist, 0*ylist, 'k:',
               x, 0, 'r.',
               'Linewidth', 3, 'Markersize', 50 );
      
    
    
      CHECK:
      Your plot should be something like hw041_noaxis.jpg:
       
 
    
SUBMIT: Your file should be named "hw041.m", and begin with:
        % hw041.m
        % YOUR NAME
        % This script (describe what it does)