### 2.24.12 Factorization : `collect`

`collect` takes as argument a polynomial or a list of polynomials and optionnaly an algebraic extension like `sqrt(n)` (for √n).
`collect` factorizes the polynomial (or the polynomials of the list) on the field of it’s coefficient (for example ℚ) or on the smallest extension containing the optional second argument (e.g. ℚ[√n]). In complex mode, the field is complexified.
Examples :

- Factorize x2−4 over the integers, input :
  `collect(x```^```2-4)`
  Output in real mode :
  `(x-2)*(x+2)`
- Factorize x2+4 over the integers, input :
  `collect(x```^```2+4)`
  Output in real mode :
  `x```^```2+4`
  Output in complex mode :
  `(x+2*i)*(x-2*i)`
- Factorize x2−2 over the integers, input :
  `collect(x```^```2-2)`
  Output in real mode :
  `x```^```2-2`
  But if you input :
  `collect(sqrt(2)*(x```^```2-2))`
  Output :
  `sqrt(2)*(x-sqrt(2))*(x+sqrt(2))`
- Factorize over the integers :

  x3−2x2+1 and x2−x

  Input :
  `collect([x```^```3-2*x```^```2+1,x```^```2-x])`
  Output :
  `[(x-1)*(x```^```2-x-1),x*(x-1)]`
  But, input :
  `collect((x```^```3-2*x```^```2+1)*sqrt(5))`
  Output :
  `((19*sqrt(5)-10)*((sqrt(5)+15)*x+7*sqrt(5)-5)* ((sqrt(5)+25)*x-13*sqrt(5)-15)*(x-1))/6820`
  Or, input :
  `collect(x```^```3-2*x```^```2+1,sqrt(5))`
  Output :
  `((2*sqrt(5)-19)*((sqrt(5)+25)*x-13*sqrt(5)-15)*(-x+1)*((sqrt(5)+15)*x+7*sqrt(5)-5))/6820`