"Tim Streater" wrote in message
.. .
In article , tim.....
wrote:

"Tim Streater" wrote in message
...
In article , Tim Watts
wrote:

Prove that: n^2-n-90=0

For n = -9 or n = 10, easy enough to do in one's head.

That's a solution

not a proof

At the time I wrote that, I hadn't seen/heard the full question. All I
heard was the equation part as reported on the Today prog.

Neither had/have I.

but there's enough information in what you posted to tell you that working
out in you head that:

n=10, will not get you full marks (or even close)

(unless maths exams have been really dummed down in the past 40 years since
I took mine)

tim