Q81. At which of the following conditions does the curve defined by the equation y2 - xy - x2 + 4 = 0 have a vertical tangent?Mathematics — NUST Mock 3 — Question 81 of 200A. x = yB. x = 2yC. x = -½yD. x = -2yPractice more Mathematics MCQs for entrance exam preparation on Examora.io.← Previous Question Next Question →