Find the coefficient of a4 in the product (1+2a)4 (2-a)5 using binomial theorem Share with your friends Share 0 Aarushi Mishra answered this 1+2a42-a5=-1+2a4a-25=-C04+C14 2a+C24 2a2+C34 2a3+C44 2a4 C05-C15 a+C25 a2-C35 a3+C45 a4-C55 a5Coefficient of a4 will be obtained when1. Constant term of first expansion is multiplied by term having a4 in second expansion 2.Term with a of first expansion is multiplied by term having a3 in second expansion3.Term with a2 of first expansion is multiplied by term having a2 in second expansion4.Term with a3 of first expansion is multiplied by term having a in second expansion5.Term with a4 of first expansion is multiplied constant term of second bracket We will only consider these 5 terms that will come on multipication of 1+2a4 and 2-a5 and neglect others as they will not contribute to coefficient of a4Term of a4 in 1+2a42-a5=-C04×C45 a4+C14 2a×-C35 a3+C24 2a2×C25 a2+C34 2a3×-C15 a+C44 2a4×C05=-5-80+240-160+16a4=-21a4Thus coefficent of a4=-21 -1 View Full Answer
