Matlab实现——Forward-substitution

 

%Program 3.1.1 (Forward-substitution)function X=forwardsub(A,B)%Input  - A is an n x n lower-triangular nonsingular  matrix%        - B is an n x 1 matrix%Output - X is the solution to the linear system AX = B%Find the dimension of B and initialize Xn=length(B); X=zeros(n,1); X(1)=B(1)/A(1,1);for k=2:1:n      X(k)=(B(k)-A(k,1:k-1)*X(1:k-1))/A(k,k);end

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A=[3,0,0,0;5,6,0,0;-4,7,-2,0;3,2,-1,4;];B=[6;4;-7;20;];X=forwardsub(A,B)