perplexus.info :: Just Math : Subtract Products, Get Identity?

Subtract Products, Get Identity? (Posted on 2007-04-11)

P and Q are two 2x2 matrices and I is a 2x2 unit matrix.

Is it ever the case that PQ - QP = I?

See The Solution Submitted by K Sengupta

Rating: 2.5000 (2 votes)

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general case

Comment 3 of 3 |

The problem works for nxn matrices, because Tr(PQ-QP)=0 and Tr(I)=n, where Tr(A)=a11+a22+...+ann

Posted by Stefan on 2007-04-26 04:45:01

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