The coefficient of y  in the expansion of (y2+ay)5  is

General expansion (y2+ay)5 is We have general term in the expansion (x+a)n (∴  Tr+1= nCr xn−r (a)r  be the expansion of (x+a)n)             Tr+1= 5Cr(y2)5−r(ay)r          Tr+1= 5Cr(y)10−2r(a)r(y−1)r                     Tr+1= 5Cr y10−3r ar.................(1) y10−3r  compare with y1 ⇒y10−3r=y1 This term contains y  if 10−3r=1  i.e. if 3r=9  ∵r=3  substitute in Eqn (1)∴   Coefficient  of y= 5C3a3                            =10a3