Exercise · ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-005 · ★★☆ Intermediate
Find the general solution of \(y'=\dfrac{x+y}{x}\) for \(x>0\).
Choose one option.
Show answer
- B. \(y=x(\ln x+C)\)
Explanation
From \(xv'=1\) we get \(v=\ln x+C\); since \(y=vx\), \(y=x(\ln x+C)\). The constant is also multiplied by \(x\).
Review the concept: First-order homogeneous equation
A first-order homogeneous equation is a differential equation in which \(y'\) is a function \(F\) of the quotient \(y/x\).
\[\frac{dy}{dx}=F\!\left(\frac{y}{x}\right),\quad v=\frac{y}{x}\;\Rightarrow\; x\,v'=F(v)-v\]
More practice problems: first-order homogeneous equation
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-001 Which of these equations is first-order homogeneous?
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-002 With y=vx, where v depends on x, what is y'?
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-003 Applying y=vx to y'=(x+y)/(x), what does xv' reduce to?
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-004 Solve y'=(y)/(x).
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-006 Solve y'=(y^2+xy)/(x^2) for x>0.
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-007 If y'=(x+y)/(x) and y(1)=2, what is y(e)?
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-008 For y'=(x^2+y^2)/(xy), what is F(v) with v=y/x?
- ZW-FIRST-ORDER-HOMOGENEOUS-EQUATION-009 Why does the substitution v=y/x work in y'=F(y/x)?
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