[" The coefficient of "x^(n)" in expansion of "(1+x)(1-x)^(n)" is "],[[" (a) "(n-1)," (b) "(-1)^(n)(1-n)," (c) "(-1)^(n-1)(n-1)^(2)," (d) "(-1)^(n-1)n],[" The coefficient of the middle term in the binomial expansion in powers of "x" of "]]