text: m² + m + 20 will not factor with rational factors\n\nThe roots to m² + m + 20 = 0 are \nm = -1/2 ± √i(79)/2 where i = √ (-1)\n\nSo it does factorise in the complex field to\nm² + m + 20 = (m + 1/2 + √i(79)/2)(m + 1/2 - √i(79)/2)\n\nHowever\nm² + m - 20 = (m + 5)(m - 4)