This fragment from a recent email from my (first year) student is the best reason why mobile phones (which now give access to Web) should remain strictly forbidden in examinations.
> for Q A5 of the 2009 paper qb
> isnt the igen vector -1,1 ?
> this is what i get from, using an online calculator found here
Yes, indeed, if the matrix [ 1 , 2\\ -2 , -3 ] from the exam is entered into the online calculator, it produces an eigenvector [-1\\ 1]; my answer that was questioned by my student was [1\\ -1]. Alas, computation, especially quick user-friendly automated computation, cannot replace understanding.