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Homogeneous & Linear Differential Equations · Question 36 of 120

Question 36

MediumOriginal question

What is the general solution of dydx=x+yx\frac{dy}{dx} = \frac{x + y}{x}?

Options for question 36

Show the answer and explanation
CorrectNot quiteAnswer B

Correct answer: B

Explanation

  1. y=vxy = vx: v+xdvdx=1+vv + x\frac{dv}{dx} = 1 + v, so dvdx=1x\frac{dv}{dx} = \frac{1}{x}.

  2. v=log⁡∣x∣+Cv = \log\lvert x \rvert + C, so y=xlog⁡∣x∣+Cxy = x\log\lvert x \rvert + Cx.

Worth noting

xlog⁡∣x∣+Cx\log\lvert x \rvert + C forgets that the constant belongs to vv and is multiplied by xx too.

Concept
Solving a homogeneous equation
Typical time
90 s
Your time
—
The rule this testsSolving homogeneous equations
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Ten questions from Homogeneous & Linear Differential Equations, at your own pace.

Practise this chapter →

Ten questions from Homogeneous & Linear Differential Equations, at your own pace.