It is= = , where = = = 84 is the corresponding coefficient of the binomial expansion, equal to the number of combinations of 9 things taken 6 at a time. On the binomial expansion read this lesson Binomial Theorem, Binomial Formula, Binomial Coefficients and Binomial Expansion. On the combinations read this lesson Introduction to Combinations. One more useful link is this lesson The Pascal's triangle in this site. Answer. The seventh term of is .
The good lady above made an error. Rule: The (r+1)st term ofis n = 9 r+1 = 7 r = 6 Substitute A=x, B=3, n=9, r=6 in the above rule The (6+1)st term of is The 7th term of is The 7th term of is Edwin