Get Answers to all your Questions

header-bg qa

Solution of diffrenrtial equation \frac{dy}{dx} = \frac{y}{ylny-x}   is 

  • Option 1)

    4xy+2y^2lny - y^2=C

  • Option 2)

    4xy+2y^2lny + y^2=C

  • Option 3)

    4xy-2y^2lny - y^2=C

  • Option 4)

    4xy-2y^2lny + y^2=C

 

Answers (1)

best_answer

As we have learned

Linear Differential Equation -

Multiply by e^{SPdx}  which is the Integrating factor

- wherein

P is the function of x alone

 

 Like \frac{dy}{dx}+ Py = Q , where P, Q are function of x alone  \frac{dx}{dy}+ Px = Q, Where P,Q

are function of y alone is also a form of linear diffrential equation . So given equation here can

be written as \frac{dx}{dy}= \frac{ylny-x}{y}

 

\frac{dx}{dy}+ x/y= lny  on compairing it with \frac{dx}{dy}+ px= Q , we get p= 1/y and Q = lny

 integrating factor e^{1/ydy}= e^{lny }= y

multiplying both sides by integrating factor , we get 

y \frac{dy}{dx}+ x = y lny

\Rightarrow \frac{d}{dy}(yx)= y lny

\Rightarrow d(xy)- y lnydy= 0

\Rightarrow\int d(xy)- \int y lnydy= c

 using integration by parts , we get , 

xy - \frac{y^2}{2}lny + \frac{y^2}{4}= C

\Rightarrow 4xy-2y^lny + y^2=C

 

 

 

 

 


Option 1)

4xy+2y^2lny - y^2=C

Option 2)

4xy+2y^2lny + y^2=C

Option 3)

4xy-2y^2lny - y^2=C

Option 4)

4xy-2y^2lny + y^2=C

Posted by

Plabita

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE