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Homogeneous & Linear Differential Equations · Question 31 of 120

Written as dy/dx = F, what is F in terms of v = y/x?

Question 31

EasyOriginal question

Consider the differential equation x2dydx=x2+xy+y2x^{2}\frac{dy}{dx} = x^{2} + xy + y^{2}, and put y=vxy = vx.

Written as dydx=F\frac{dy}{dx} = F, what is FF in terms of v=yxv = \frac{y}{x}?

Options for question 31

Show the answer and explanation
CorrectNot quiteAnswer C

Correct answer: C

Explanation

  1. Divide the right side by x2x^{2}: 1+yx+y2x21 + \frac{y}{x} + \frac{y^{2}}{x^{2}}.

  2. F=1+v+v2F = 1 + v + v^{2}.

Worth noting

1+v21 + v^{2} is what is left after the vv cancels in the next step, not FF itself.

Concept
Recognising a homogeneous equation
Typical time
90 s
Your time
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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.