# Talk:06-240/Classnotes For Thursday November 16

From Drorbn

When we perform Gaussian Eliminations, sometimes, we can

(i) do multiple operations at a time, if they do not "affect" each other (i.e. eliminate all the entries below a 1 in one step),

(ii) replace a row with a multiple of the row plus a multiple of anther row--i.e. R1 := aR1+bR2 (which is simply a combination of two elementary operations), and

(iii) if we see that two equations are obviously the same early on, eliminate them right away even if it is not the step prescribed by the algorithm.

Are we allowed to take these shortcuts in our assignment/exam work?

(There are probably more common sense shortcuts that I have not listed.)

Yes, these are fine. Note though that your (ii) works only if . --Drorbn 08:58, 20 November 2006 (EST)