Question: Maple number comparison of square roots

I've created som Maple-code to determine if for all entrances in a quadratic matrix, D, the inequality d_i,j <= d_{i,k +} d_k,j is true.

it works correctly I think. However if I call isDistance on a matrix with square root elements (I use sqrt(some number)) I get the error:

Error, (in isDistance) cannot determine if this expression is true or false: 2*474^(1/2) < 0
I've tried unsuccessfully using absolute values before I compare. What goes wrong and what should I change?

The error-link introduces a single-quote operator which I've tried applying but without success.