Please help me with #6-8

6. Solve mathematically for n: (2 )- (20 ) - 44 7. In the binomial expansion of (1+ kx) where k is a constant, the coefficient of x is twice as large as the coefficient of x2. Find the value of k. 8. Given f(x) = 4x+ 1 where k is a positive constant. Given the coefficient of x in the binomial kx expansion of f(x) is 21, determine the value of k