My problem is that I'm going through a practice exam and my answer does not match any of the choices. Please help me to determine if my formula is incorrect. Thanks in advance!

Use the Binomial Theorem to find the 3rd term of (4x+3y)^9

3=2+1, thus k = 2, a = 4x, b = 3y, n = 9

9!/(2!7!)*4x^7*3y^2

My answer = 5308416x^7y^2

However, the answers are:

a) 419,894x^7y^2; b) 314,928x^7y^2, c) 419,904x^2y^8, or d) 1,259,712x^2y^7

Please tell me what I'm doing wrong, I just don't get it...