(i) (a_1=243), (r=\dfrac{1}{3})

[ 243,\ 81,\ 27,\ 9,\ 3 ]

(ii) (a_1=579), (r=-\dfrac{1}{2})

[ 579,\ -\dfrac{579}{2},\ \dfrac{579}{4},\ -\dfrac{579}{8},\ \dfrac{579}{16} ]