Q166. The lines a1x + b1y + c1 = 0 and a2x + b2y + c2 = 0 are parallel if and only if:Mathematics — Analytic Geometry — Question 166 of 217A. a1b2 + a2b1 = 0B. a1b2 - a2b1 = 0C. a1a2 + b1b2 = 0D. a1a2 - b1b2 = 0Practice more Mathematics MCQs for entrance exam preparation on Examora.io.← Previous Question Next Question →