# A question on linear algebra(also Matlab related)

1. Jun 23, 2014

### mech-eng

Hi, Can someone explain me the division operation in the picture. First for left division we use (.\ ) not only ( \ ) And it is strange that when we divide first column of A by first column of B( here first column of B is 44) how can we find -5.1250 ?

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Last edited: Jun 23, 2014
2. Jun 23, 2014

### micromass

Staff Emeritus
3. Jun 23, 2014

### mech-eng

4. Jun 23, 2014

### MarneMath

That just happens to be what matlab calls the method that solves the linear system. A person could also write it as mldivide(A,b). Also, in matlab A.\B nd A\B are equivalent statements. Try it out.

5. Jun 26, 2014

### HallsofIvy

Staff Emeritus
That's NOT standard notation. If Ax= b (and A is invertible) then $x= A^{-1}b$. if xA= b then $x= bA^{-1}$. Because standard division (a/b) does not distinguish between "divide on the left" and "divide on the right" we don't normally use that notation.

That particular author (and possibly math lab- I don't use it) is using a special notation to distinguish between "division on the left" ($A^{-1}b$) and "division on the right" ($bA^{-1}$).