1. Consider the function f(x) = -2.75x3 + 18x - 21x - 12 a) Plot the graph of f(x) in MATLAB and find all the roots of the function f(x) graphically. Provide the code and the plot you obtained. b) Compute by hand the first root of the function with the bisection method, on the interval (-1; 0] for a stopping criterion of 1%. c) How many iterations on the interval [-1, 0] are needed with the bisection method to obtain the true error of the first root less than 10-8? d) Find all the roots applying MATLAB's built-in procedure. Include the MATLAB code used and the output obtained.