Find the fifth term in the expansion of (4-1/5x)^9 in ascending powers of x

Answer 1

You must know the binomial expansion and the general term of the expansion!!

5th term = C(9,4) (4^4)(-x/5)^5
= 126 (256)(-x^5)/3125
= -32256/3125 x^5

oops, just did in descending powers, so

C(9,5) 4^5 (-x/5)^4
= 126(1024)(x^4/625)
= 129024/625 x^4 , in ascending order