rat(q) gives (2*sqrt(17)+1)/16. factor(q), ratsimp(q) ... give quotient by zero expand(q) gives 0.



q: -((((-1 + sqrt(17))**2 - ((-3 + sqrt(17))*(5 + 3*sqrt(17)))/2)*
           (((-1 + sqrt(17))**2*(4 + sqrt(17)))/4 -
             ((5 + sqrt(17))*(5 + 3*sqrt(17)))/8))/
         (-1 - 8*(4 + sqrt(17)) + (4 + sqrt(17))**2)**2);

expand(q) gives 0
rat(q) gives (2*sqrt(17)+1)/16
ratsimp, factor, radcan, give quotient by zero.

(example taken from report in mathematica news group. Mathematica is
similarly befuddled.)

RJF