System solving using rref

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Abdulaziz Aljaber
评论： Walter Roberson 2018-9-6
Hello,
So I am trying to write a system solving script using rref. Matrix and vector, A and B, are given already. What is needed is solving the 3 equation, also given, and produce an output file that looks like screenshot 1, but instead i get an output of screenshot 2. And I apologize for not including the code into the body, but i have no clue how to do it properly.
Thanks
  2 个评论
madhan ravi
madhan ravi 2018-9-6
just upload your code instead of a screenshot
Abdulaziz Aljaber
Abdulaziz Aljaber 2018-9-6
Just did! didnt know they had a code button that does it for you.

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回答（2 个）

Abdulaziz Aljaber
load ('A');
load ('B');
rref(A);
rref(B);
syms a b c d x y z
Eq1 = 1*x + (-2*y) + 3*z == 7;
Eq2 = 2*x + 1*y + 1*z == 4;
Eq3 = -3*x + 2*y + -2*z == 1;
fprintf('Equation 1 is: 7 %6.4f\n','Equation 2 is: %6.4f\n', 'Equation 3 is:%6.4f\n')
fprintf('The solutions are as follows: %n', x, y, z)
fid=fopen('output data.txt','wt');
fprintf(fid, '%f %f r\n');
fclose(fid);
  1 个评论
Abdulaziz Aljaber
Abdulaziz Aljaber 2018-9-6
this is what i get as a result
Equation 1 is: 7 69.0000
Equation 1 is: 7 113.0000
Equation 1 is: 7 117.0000
Equation 1 is: 7 97.0000
Equation 1 is: 7 116.0000
Equation 1 is: 7 105.0000
Equation 1 is: 7 111.0000
Equation 1 is: 7 110.0000
Equation 1 is: 7 32.0000
Equation 1 is: 7 50.0000
Equation 1 is: 7 32.0000
Equation 1 is: 7 105.0000
Equation 1 is: 7 115.0000
Equation 1 is: 7 58.0000
Equation 1 is: 7 32.0000
Equation 1 is: 7 37.0000
Equation 1 is: 7 54.0000
Equation 1 is: 7 46.0000
Equation 1 is: 7 52.0000
Equation 1 is: 7 102.0000
Equation 1 is: 7 92.0000
Equation 1 is: 7 110.0000
Equation 1 is: 7 69.0000
Equation 1 is: 7 113.0000
Equation 1 is: 7 117.0000
Equation 1 is: 7 97.0000
Equation 1 is: 7 116.0000
Equation 1 is: 7 105.0000
Equation 1 is: 7 111.0000
Equation 1 is: 7 110.0000
Equation 1 is: 7 32.0000
Equation 1 is: 7 51.0000
Equation 1 is: 7 32.0000
Equation 1 is: 7 105.0000
Equation 1 is: 7 115.0000
Equation 1 is: 7 58.0000
Equation 1 is: 7 37.0000
Equation 1 is: 7 54.0000
Equation 1 is: 7 46.0000
Equation 1 is: 7 52.0000
Equation 1 is: 7 102.0000
Equation 1 is: 7 92.0000
Equation 1 is: 7 110.0000
The solutions are as follows: >>

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Walter Roberson
Walter Roberson 2018-9-6
fprintf('Equation 1 is: %s\nEquation 2 is: %s\nEquation 3 is: %s\n', Eq1, Eq2, Eq3);
fprintf('The solutions are as follows:\n');
Now calculate the solutions and store them in variables X, Y, and Z, then:
fprintf('x = %.4f\ny = %.4f\nz = %.4n\n', X, Y, Z)
I recommend that you do not store the solutions in variables x, y, and z, as that gets confusing against the use of x, y, and z as symbolic variables.
  2 个评论
Abdulaziz Aljaber
Abdulaziz Aljaber 2018-9-6
Okay that is better, but is there a way to let matlab solve it for me? because that is what is asked for.
Walter Roberson
Walter Roberson 2018-9-6
We have no information about relationship A and B have to the rest of the question.
My guess is you want something like
for row = 1 : size(A,1)
fprintf('Equation %d is: %5fx + %5fy + %5fz = %5f\n', A(row,:), B(row));
end
and that you want to use rref() to solve the system
A*[x;y;z] = B
It is easy to do, taking only a few characters, but figuring out how is an important part of the homework.

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