N2026 P1 Q4

N2026 P1 Q4

Junior College 2
6 marks
  1. Use the substitution \(y=vx\) to show that the differential equation
    \[x^2\frac{\mathrm{d}y}{\mathrm{d}x}=y^2+xy\]
    reduces to
    \[x\frac{\mathrm{d}v}{\mathrm{d}x}=v^2.\][3]
  2. Hence find the general solution of the differential equation
    \[x^2\frac{\mathrm{d}y}{\mathrm{d}x}=y^2+xy.\]
    Give your answer in the form \(y=\mathrm{f}(x)\), where \(\mathrm{f}(x)\) is a function to be determined.[3]
Answer:(a) Shown (b) \(y=-\dfrac{x}{\ln\left|x\right|+C}\), where \(C\) is an arbitrary constant

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