\%Return the agumented A and b after applying \%the forward elemination step(s) of Gauassian elimination \%to A and b. \%You may use Matlab's size and zeros functions, but no other \%Matlab functions can be used to implement this function. function [A,b]= forwardelimination (A,b) end \%Return x, the solution to linear system Ax=b, by \%using backward substitution. This function assumes \%A is a n by n uppertriangular matrix and %b is a n by 1 matrix. \%You may use Matlab's size and zeros functions, but no other \%Matlab functions can be used to implement this function. function [x]= backwardsubstitution (A,b) end \%Return r, the residual (error) vector, where %r=bAx. You may use matrix operators {+,,} \%to implement this function. function [r]= residualvector (A,x,b)