⇒x2+1+2x+4x2+4−8x+1+9x2+6x=20 ⇒14x2+6=20⇒14x2=14 ⇒x2=1⇒x=±1 but x must be positive as in question conditions i.e. x>0. ∴‌‌x=−1 (Rejected) Hence, x=1 ∴‌‌y=2x=2×1=2 Now, OP, OQ and OR are coplanar. ∴‌‌[OP‌OQ‌OR]=0