By virtue of Baileys well-known bilateral 6psi_6 summation formula and Watsons transformation formula,we extend the four-variable generalization of Ramanujans reciprocity theorem due to Andrews to a five-variable one. Some relevant new q-series ident
ities including a new proof of Ramanujans reciprocity theorem and of Watsons quintuple product identity only based on Jacksons transformation are presented.
With the use of the $(f,g)$-matrix inversion under specializations that $f=1-xy,g=y-x$, we establish an $(1-xy,y-x)$-expansion formula. When specialized to basic hypergeometric series, this $(1-xy,y-x)$-expansion formula leads us to some expansion fo
rmulas expressing any ${}_{r}phi_{s}$ series in variable $x~t$ in terms of a linear combination of ${}_{r+2}phi_{s+1}$ series in $t$, as well as various specifications. All these results can be regarded as common generalizations of many konwn expansion formulas in the setting of $q$-series. As specific applications, some new transformation formulas of $q$-series including new approach to the Askey-Wilson polynomials, the Rogers-Fine identity, Andrews four-parametric reciprocity theorem and Ramanujans ${}_1psi_1$ summation formula, as well as a transformation for certain well-poised Bailey pairs, are presented.
