"Farmer Giles" wrote in message
...
On 06/06/2015 19:07, tim..... wrote:

"Farmer Giles" wrote in message
...
On 06/06/2015 11:15, 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

tim




Correct, it is not a proof - neither was my answer earlier.

This is, though: 6/n x 5/n-1 = 1/3

-- 30/n^2-n = 1/3

-- 90 = n^2-n -- 0 = n^2-n-90

but it's still not a proof in the context of a maths question, which is

prove that n = 10 (from the information in the question, not from the
equation)


It didn't ask me to solve for n - but I have done. I formed the equation
from the information in the question - thereby proving it. And, in my
previous reply, I derived that n=10 from the equation.

you're right sorry