- #1
SurferStrobe
1. Evaluate the numbers for the coefficient of x4y9 in the expansion of (3x + y)13.
2. The Binomial Theorem states that for every positive integer n,
(x + y)n = C(n,0)xn + C(n,1)xn-1y + ... + C(n,n-1)xyn-1 + C(n,n)yn.
3. I understand that the coefficients can be found from the n row of Pascal's triangle, where n = 13. Using the binomial theorem, my approach (which I'm not sure about) is:
The coefficient is 3 * C(13,9) = 3 * 715 = 2145.
Am I going about this correctly? Sorry if I didn't expand on the proof.
surferstrobe
2. The Binomial Theorem states that for every positive integer n,
(x + y)n = C(n,0)xn + C(n,1)xn-1y + ... + C(n,n-1)xyn-1 + C(n,n)yn.
3. I understand that the coefficients can be found from the n row of Pascal's triangle, where n = 13. Using the binomial theorem, my approach (which I'm not sure about) is:
The coefficient is 3 * C(13,9) = 3 * 715 = 2145.
Am I going about this correctly? Sorry if I didn't expand on the proof.
surferstrobe