Hi,

there are several posts on the topics of having matrices with "variable" entries in this forum, but all date back at least 6 years and none of them helped me with my current problem: Given an upper-diagonal matrix with some entries that are variable I want to multiply this matrix with another one in order to make the calculation of the determinant more challenging:

```
Context('Matrix')->variables->are('x'=>'Real', 'y'=>'Real', 'z'=>'Real');
foreach $i (0..4) {
foreach $j (0..4) {
$a[$i][$j] = non_zero_random(-9,9,1);
}
}
$A = GL4Z();
$Ainv = $A->inverse;
$M = Matrix([[ 'x', 'x^2', $a[0][2], $a[0][3]],
[ 0, 'y', 'y^2', $a[1][3]],
[ 0, 0, 'z', 'z^3'],
[ 0, 0, 0, $a[3][3]]]);
$AMAinv = Formula("($A * $M * Ainv)")->reduce;
$ans = Compute("x * y * z * $a[3][3]");
Context()->texStrings;
BEGIN_TEXT
Find the derivative of the function
\[ f(x) = \det $AMAinv . \]
```

What do you recommend? Is there another way other than hardcoding the product?

Best wishes, Fabian