rootof ???

[Helge Gabert]

I recently ran into this (in CAS):

solve(x^2-2*x+((-1-i)*x)/sqrt(2)+(2+2*i)/sqrt(2),x) returns

{2,-1/12*rootof([[1 -3 -5 3] [1 0 -2 0 9]])}

Question: What is rootof? (needless to say, not mentioned in the documentation)

The whole construct seems weird. The argument to rootof (a 2x4.5 matrix?) has four columns in the first row and 5 columns in the second. Indeed, if I try to copy this from the history line, the prime issues an error message.

However, the expression to solve for has, of course, the solution {2, sqrt(i)}, as can be verified by running fsolve or proot on the expression at the top.

By the bye, a similar situation occurs by running collect().