If the chord joining the points \(P_1\left(x_1, y_1\right)\) and \(P_2\left(x_2, y_2\right)\) on the parabola \(y^2=12 x…

If the chord joining the points \(P_1\left(x_1, y_1\right)\) and \(P_2\left(x_2, y_2\right)\) on the parabola \(y^2=12 x\) subtends a right angle at the vertex of the parabola, then \(x_1 x_2-y_1 y_2\) is equal to

[JEE Main 2026, 22 Jan (Shift 1)]