(a) $AB = A + B$ $\Rightarrow B = AB - A = A(B - I)$ $\Rightarrow$det$(B) = \det(A)\det(B - I) = 0$ $\Rightarrow$det $(B) = 0$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.