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Re:Don’t invert that matrix (2010) by JadeNB on Thursday May 12, 2016 @05:19PM (#11686856)
I think that the idea is not that you don't take steps that, taken together, amount to inverting `A`, but rather that you don't just try to invert `A`. Thus, I think that the idea is to do something like "Compute `A = LU`, and then invert `L` and `U`"—which of course can be used to invert `A`, but which isn't exactly the same as "Compute `A^{-1}`" (using Cramer's rule, or some other absurdity).

Incidentally, while solving `Ax = b` in general is definitely equivalent to inverting `A` (simply by taking `b` to be basis vectors, so that the solutions `x` are the columns of the inverse matrix in that basis), it is certainly possible to solve it in particular cases without inverting `A`; for example, the solution to `Ax = b`, where `b` is the first column of `A` in a particular basis, is the first vector `x` of that basis—no inversion required (nor even computation of `b`)!

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