1.将下列函数展开成x的幂级数,并求其成立的区间:-|||-(1) (x)=ln (a+x) ;-|||-(2) (x)=(a)^x ;-|||-(3) (x)=(e)^-(x^2) ;-|||-(4) (x)=(cos )^2x ;-|||-(5) (x)=dfrac (x)(sqrt {1+{x)^2}} ;-|||-(6) (x)=dfrac (x)({x)^2-2x-3}