Unexpected result calculating the determinant of a singular matrix (42S)

[Werner]

(10-23-2019 11:06 PM)Valentin Albillo Wrote:  

Quote:A 7x7 matrix with integer elements less than 100 and determinant 1 will always have at least 1 digit correct when the calculations are done with 15 digits

I can't try and find a counterexample to what you state because I don't have an HP48-whatever to check if my attempts work or not so I'll take your word for it.

Suppose you calculate the determinants using Cramer's rule. The intermediate products would then be no larger than 100^7 = 1e14, the final result being 1 - so you'll lose at most 14 digits. I think ;-)

Cheers, Werner