Let a,bāZ which are not perfect squares. Prove that if x^2 \minus{} ay^2 \minus{} bz^2 \plus{} abw^2 \equal{} 0 has a nontrivial solution in integers, then so does x^2 \minus{} ay^2 \minus{} bz^2 \equal{} 0. number theoryDiophantine equationquadraticsequationIMO Shortlist