Auxiliary equation: dxP = dyQ = dzR ⇒ dxx2 = dyy2 = dzz2 Group-I dxx2 = dyy2 ∫dxx2 = ∫ dyy2 ⇒-1x = -1y + c1 ⇒1y - 1x = c1 Group-II dyy2 = dzz2 ∫dyy2 = ∫ dzz2 ⇒-1y = -1z + c2 ⇒1z - 1y = c2 Solution: f 1y - 1x , 1z - 1y = 0