GIA'I PHU.O.NG TRNH VI PH^AN XY” + 2Y0−XY=EX BANG PHEP D^O'I HAM...

176)

Gia'i phu.o.ng trnh vi ph^an

^{xy” + 2y}

⁰

^−xy=e

^x

bang phep d^o'i ham

^{z =xy}

.

HD gia’i:

D - a.t

^{z =xy ⇒z}

⁰

^=y+xy

⁰

^;z

⁰⁰

^{= 2y}

⁰

^+xy

⁰⁰

. Thay vao phu.o.ng trnh:

z

⁰⁰

−z =e

^x

→NTQ z =C

1

+C

2

e

^x

Nghi^e.m ri^eng da.ng:

^y=Axe

^x

^{→A= 1}₂

V^a.y:

^{y= z}_x ⁼ _x^1(C

¹

^+C

²

^e

^x

⁺¹₂^xe

^x

⁾x

ⁿ⁺¹