The coefficients for the binomial expansion [tex](a+b)^n[/tex] are symmetric across the middle term.
For the binomial expansion [tex](x+y)^{10}[/tex] you will get 10+1=11 coefficients. The 6th term is middle term. If the coeeficients are
1, 10, 45, 120, 210, 252, 210, B, 45, 10, 1,
then the 6th term is 252.
This means that
- 5th and 7th terms are the same;
- 4th and 8th terms are the same;
- 3rd and 9th terms are the same;
- 2nd and 10th terms are the same;
- 1st and 11th terms are the same.
If 4th and 8th terms are the same, then B=120.
Answer: correct choice is D
