Straight Lines And Pair Of Straight Lines

Let \(\mathrm{PQR}\) be a right angled isosceles triangle, right angled at \(\mathrm{P}(2,1)\). If the equation of the line \(\mathrm{QR}\) is \(2 x+y=3\), then the equation representing the pair of lines \(P Q\) and \(P R\) is