香港巴士論壇

1.Prove by M.I that 5^n (4n-1) +1 is divisable by 16 for all positive integer n.


2. Let n be a positive integer.

a) If (1+px+x^2)^n = 1+ax + bx^2 +cx^3 + terms involvoing higher powers of x , express a,b,c in term of p and n.

b)If the coefficients of x and x^2 in the expansion of (1+px+x^2)^n are 14 and 91 respectively, find the value of p and n.

c) Hence find the coefficient of x^3.

thx sosad