Need help on solving this bisection method question

: Given the equation 𝑓(𝑥) = −2𝑥^6 − 1.6𝑥^4 + 12𝑥 + 1

Write a code to use the bisection method to calculate the maximum between [0,1]. Iterate until the approximate absolute error falls below 5%. Print the root and number of iterations on the screen.

I've done this so far with the script but I don't know where to go from here. Please help.

syms x
f(x)=-2*x^6-1.6*x^4+12*x+1;
dfdx= diff(f,x);

a=0;
b=1;
i=0;
err=1000;

while err>0.05
    c=(a+b)/2
    if double((dfdx(a)))*double((dfdx(c)))<0
        a=c
    else
        b=c
    end
    err=;
    i=i+1;
end
fprintf('The max of equation in [0,1] is %f by %d',c, i)

Answer 1

[Alan Stevens]

You really don't need any symbolic parameters here; and you had the logic with a and b the wrong way round! Try

f = @(x) -2*x.^6-1.6*x.^4+12*x+1;
dfdx= @(x) -12*x.^5 - 6.4*x.^3 + 12;

a=0;
b=1;
i=0;
err=1000;

while err>0.05 
    c=(a+b)/2;
    if dfdx(a)*dfdx(c)<0
        b=c;
    else
        a=c;
    end
    err = abs(dfdx(c));  % Assuming the error is in the gradient  
    i=i+1;
end
fprintf('The max of equation in [0,1] is %f in %d iterations',f(c), i)