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Question Number 193733 by Tawa11 last updated on 18/Jun/23
Find the ordinary differential equation  satisfy by:                       y  =  x^n (A  +  Blogx)
$$\mathrm{Find}\:\mathrm{the}\:\mathrm{ordinary}\:\mathrm{differential}\:\mathrm{equation} \\ $$$$\mathrm{satisfy}\:\mathrm{by}: \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\mathrm{y}\:\:=\:\:\mathrm{x}^{\mathrm{n}} \left(\mathrm{A}\:\:+\:\:\mathrm{Blogx}\right) \\ $$
Answered by Rajpurohith last updated on 19/Jun/23
y ′=x^n ((B/x))+nx^(n−1) (A+Blog(x))  =Bx^(n−1) +((n/x))y  ⇒xy ′=Bx^n +ny....(1)  differentiate again  xy′′+y^′ =Bx^(n−1) +ny′  ⇒x^2 y′′+xy′=Bx^n +nxy′....(2)  subtract (1) from (2)  x^2 y′′+xy′−xy′=Bx^n +nxy′−Bx^n −ny  ⇒x^2 y′′−nxy′+ny=0  is the required ODE.
$${y}\:'={x}^{{n}} \left(\frac{{B}}{{x}}\right)+{nx}^{{n}−\mathrm{1}} \left({A}+{Blog}\left({x}\right)\right) \\ $$$$={Bx}^{{n}−\mathrm{1}} +\left(\frac{{n}}{{x}}\right){y} \\ $$$$\Rightarrow{xy}\:'={Bx}^{{n}} +{ny}….\left(\mathrm{1}\right) \\ $$$${differentiate}\:{again} \\ $$$${xy}''+{y}^{'} ={Bx}^{{n}−\mathrm{1}} +{ny}' \\ $$$$\Rightarrow{x}^{\mathrm{2}} {y}''+{xy}'={Bx}^{{n}} +{nxy}'….\left(\mathrm{2}\right) \\ $$$${subtract}\:\left(\mathrm{1}\right)\:{from}\:\left(\mathrm{2}\right) \\ $$$${x}^{\mathrm{2}} {y}''+{xy}'−{xy}'={Bx}^{{n}} +{nxy}'−{Bx}^{{n}} −{ny} \\ $$$$\Rightarrow{x}^{\mathrm{2}} {y}''−{nxy}'+{ny}=\mathrm{0} \\ $$$${is}\:{the}\:{required}\:{ODE}. \\ $$$$ \\ $$
Commented by Tawa11 last updated on 19/Jun/23
I appreciate sir.  God bless you.
$$\mathrm{I}\:\mathrm{appreciate}\:\mathrm{sir}. \\ $$$$\mathrm{God}\:\mathrm{bless}\:\mathrm{you}. \\ $$

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