1969 Canadian MO Problems/Problem 7

Revision as of 09:22, 29 April 2008 by 1=2 (talk | contribs) (Useless links)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

Problem

Show that there are no integers $a,b,c$ for which $a^2+b^2-8c=6$.

Solution

Note that all perfect squares are equivalent to $0,1,4\pmod8.$ Hence, we have $a^2+b^2\equiv 6\pmod8.$ It's impossible to obtain a sum of $6$ with two of $0,1,4,$ so our proof is complete.

References

1969 Canadian MO (Problems)
Preceded by
Problem 6
1 2 3 4 5 6 7 8 Followed by
Problem 8