The sum of the coefficients in the expansion of (5χ - 4y)n , where n is a positive integer is

1) 0 

2) n

3) 1

4) - 1  

6. What is the coefficient of I'y in the expansion of (x + y)'? Obtain a single number.

What is the coefficient of x⁴ in the binomial expansion of (x+3)¹²?

What is the coefficient of the last term in the binomial expansion of (x+1)⁹?