Science:Math Exam Resources/Courses/MATH152/April 2011/Question A 21
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Question A 21 

Suppose that is a invertible matrix and is a column vector with 12 entries. Both and have been entered into MATLAB. What command(s) would you use to compute the vector that solves the linear system

Make sure you understand the problem fully: What is the question asking you to do? Are there specific conditions or constraints that you should take note of? How will you know if your answer is correct from your work only? Can you rephrase the question in your own words in a way that makes sense to you? 
If you are stuck, check the hint below. Consider it for a while. Does it give you a new idea on how to approach the problem? If so, try it! 
Hint 

Which symbol does Matlab use to indicate a leftdivision? Is is a good idea to invert ? 
Checking a solution serves two purposes: helping you if, after having used the hint, you still are stuck on the problem; or if you have solved the problem and would like to check your work.

Solution 

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Please rate my easiness! It's quick and helps everyone guide their studies. One would use the backslash operator '\', and store the answer into a vector called . The full command in your MATLAB console would look like x = A\b; Note that x = inv(A)*b; would also work, but requires to compute the inverse of first. There is better ways of solving than that, and x= A\b is one of them. It does not use the inverse matrix (which is costly to compute). 