Problem: The sum of the numerical coefficients in the expansion of the binomial (a+b)6(a+b)^{6}(a+b)6 is:
Answer Choices:
A. 323232
B. 161616
C. 646464
D. 484848
E. 777 Solution:
Let a=b=1a=b=1a=b=1. Then (1+1)6=26=64(1+1)^{6}=2^{6}=64(1+1)6=26=64;
or
1+6+15+20+15+6+1=641+6+15+20+15+6+1=641+6+15+20+15+6+1=64.