Question

Решить уравнение:
y'-2xy-xy^2=0

Answer 1

Ответ:

$y'-2xy-xy^2=0\\\\y'-2xy=xy^2\\\\\star \ \ y=uv\ \ ,\ \ y'=u'v+uv'\\\\u'v+uv'-2x\cdot uv=x\cdot (uv)^2\\\\u'v+u\cdot (v'-2x\cdot v)=x\cdot u^2v^2\\\\a)\ \ v'-2x\cdot v=0\ \ ,\ \ \dfrac{dv}{dx}=2x\cdot v\ \ ,\ \ \ \int \dfrac{dv}{v}= \int 2x\, dx\ \ ,\ \ \ ln|v|=x^2\ \ ,\\\\{}\ \ \ \ v=e^{x^2}$

$b)\ \ u'v=x\cdot u^2v^2\ \ \ ,\ \ \ u'=x\cdot u^2v\ \ ,\ \ \ \dfrac{du}{dx}=x\cdot e^{x^2}\cdot u^2\ \ \ ,\ \ \ \int \dfrac{du}{u^2}=\int x\cdot e^{x^2}\, dx\ \ ,\\\\\\\int \dfrac{du}{u^2}=\dfrac{1}{2}\int e^{x^2}\cdot d(x^2)\ \ ,\ \ \ -\dfrac{1}{u}=\dfrac{1}{2}\cdot e^{x^2}+\dfrac{C}{2}\ \ ,\ \ \ -\dfrac{1}{u}=\dfrac{e^{x^2}+C}{2}\ \ ,\\\\\\u=-\dfrac{2}{e^{x^2}+C}\\\\\\c)\ \ y=uv\ \ ,\ \ y=e^{x^2}\cdot \dfrac{-2}{e^{x^2}+C}\ \ ,\ \ \ y=-\dfrac{2\cdot e^{x^2}}{e^{x^2}+C}$