First order ODEs

Bernouli differential equations

A Bernouli ODE is a first-order, non-linear ODE with the standard form

𝑑𝑦𝑑π‘₯+𝑓(π‘₯)𝑦=𝑔(π‘₯)𝑦𝑛

which in the case of 𝑛 =0 is a First-order linear differential equation; and for 𝑛 =1 is a separable differential equation. In all other cases, the ODE may be made linear by using a 𝑀-substitution:

𝑀=𝑦1βˆ’π‘›βŸΉπ‘‘π‘€π‘‘π‘₯=(1βˆ’π‘›)π‘¦βˆ’π‘›π‘‘π‘¦π‘‘π‘₯βŸΉπ‘‘π‘¦π‘‘π‘₯=(1βˆ’π‘›)βˆ’1𝑦𝑛𝑑𝑀𝑑π‘₯

which when entered into the original ODE gives

(1βˆ’π‘›)βˆ’1𝑦𝑛𝑑𝑀𝑑π‘₯+𝑓(π‘₯)𝑦=𝑔(π‘₯)𝑦𝑛𝑑𝑀𝑑π‘₯+(1βˆ’π‘›)𝑓(π‘₯)𝑦1βˆ’π‘›=(1βˆ’π‘›)𝑔(π‘₯)𝑑𝑀𝑑π‘₯+(1βˆ’π‘›)𝑓(π‘₯)𝑀=(1βˆ’π‘›)𝑔(π‘₯)

which is linear for 𝑀.

Practice problems


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