Recent content by squids

ya i used it but what should be the nth term...i have no idea...pls give me some..

i used the general term as tr=C(n,r) a^(n-r)*x^r. however i could not hav a final answer as i supposed this method is not approate so there may be other wayz to solve. and using above formula i always got the answer without the appropriate sign..could anyone help for it..

what will be the coefficient of the x^n in the expansion of (1+x)^-1 and(1-x)^-1. Please answer it separately..