Find the Taylor Series: 6/x at a=-4?

f(x)=6/x and the series is centered at a=-4. I'm not sure how to get the series in terms of n at the end and am just pretty all around confused! :) Thanks! Also, I had to find the Taylor series for 4cos(x) at a=3pi. I got 4((-1)^n)(x-3pi)^2n/(2n)! but that was wrong. Any ideas why?? Thanks so much!