en la comparant avec l’équation (H) du no 16, on aura
![{\displaystyle \varphi (x)=\beta x^{p}+\gamma x^{p+q}+\delta x^{p+2q}+\varepsilon x^{p+3q}+\ldots \,;}](https://wikimedia.org/api/rest_v1/media/math/render/svg/7191a3adf5b07ae897cdb69d9ffff2e8bca240ec)
donc
![{\displaystyle {\frac {\varphi (\alpha y)}{\alpha }}=\beta \alpha ^{p-1}y^{p}+\gamma \alpha ^{p+q-1}y^{p+q}+\delta \alpha ^{p+2q-1}y^{p+2q}+\ldots }](https://wikimedia.org/api/rest_v1/media/math/render/svg/38d38b0430b60c383f39c067b2096a2db3d1d82e)
et
![{\displaystyle {\frac {1}{1-z{\cfrac {\varphi (\alpha y)}{\alpha }}}}={\frac {1}{1-\beta \alpha ^{p-1}y^{p}z-\gamma \alpha ^{p+q-1}y^{p+q}z-\ldots }}.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/74f68f2a3fac7935d0781998d6205965c31c7caa)
Faisons, pour plus de simplicité,
![{\displaystyle \alpha ^{p-q-1}y^{p-q}z=u,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/5861aa5c409668a35581e377763b44b2a1d4adc5)
et l’on aura la fraction
![{\displaystyle {\frac {1}{1-\beta u(\alpha y)^{q}-\gamma u(\alpha y)^{2q}-\delta u(\alpha y)^{3q}-\ldots }},}](https://wikimedia.org/api/rest_v1/media/math/render/svg/bff867a9ed78002f1607208d257ed342616bbe04)
laquelle, étant développée suivant les puissances de
deviendra
![{\displaystyle 1-\mathrm {P} (\alpha y)^{q}+\mathrm {Q} (\alpha y)^{2q}+\mathrm {R} (\alpha y)^{3q}+\mathrm {S} (\alpha y)^{4q}+\ldots ,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/f64af2a8b594e67641b40b77d20b8025c61959d9)
où l’on aura
![{\displaystyle {\begin{aligned}\mathrm {P} =&\beta u,\\\mathrm {Q} =&\mathrm {P} \beta u+\gamma u,\\\mathrm {R} =&\mathrm {Q} \beta u+\mathrm {P} \gamma u+\delta u,\\\mathrm {S} =&\mathrm {R} \beta u+\mathrm {Q} \gamma u+\mathrm {P} \delta u+\varepsilon u,\\\ldots &\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots ,\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/8b4fe75f5af9a675e982a2bcff63d61013b66d0c)
et, développant de nouveau ces valeurs suivant les puissances de ![{\displaystyle u,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/30dcc93e14b40416ed2d1391bc6c08ee99fa5ff6)
![{\displaystyle {\begin{aligned}\mathrm {P} =&\mathrm {A} u,\\\mathrm {Q} =&\mathrm {B} u+\mathrm {B} _{1}u^{2},\\\mathrm {R} =&\mathrm {C} u+\mathrm {C} _{1}u^{2}+\mathrm {C} _{2}u^{3},\\\mathrm {S} =&\mathrm {D} u+\mathrm {D} _{1}u^{2}+\mathrm {D} _{2}u^{3}+\mathrm {D} _{3}u^{4},\\\mathrm {T} =&\mathrm {E} u+\mathrm {E} _{1}u^{2}+\mathrm {E} _{2}u^{3}+\mathrm {E} _{3}u^{4}+\mathrm {E} _{4}u^{5},\\\ldots &\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots ,\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/45c380bf0f6158b2256d58ee5540fa8f1973bf45)