This article is a revised version of a talk given to the Mathematics Club at the Technion, Israel's Technological University and subsequently printed in Etgar-Gilianot Mathematica, the Israeli version of Parabola.
In everyday life we tend to trust the numbers which come out of a computer or calculator.
The development of quantum mechanics earlier this century was a joint effort by a number of physicists, of whom E. Schrödinger and W. Heisenberg figure prominently.
Q.817 Find all integers $x,y$ such that $x(3y-5) = y^2+1$.