Apply each of the substitutions \(u=\frac{y}{t}\) and \(u=at+by+c\) to one of the following ODEs, and show that each result is separable. (Do not fully solve either ODE.)

  1. \( -\frac{3}{3 \, t - y + 3} = -3 \, t + y - {y'} - 6 \)
  2. \( t y {y'} = -3 \, t^{2} - y^{2} \)

Answer:

  1. \( \frac{u {u'}}{u^{2} - 3} = 1 \)
  2. \( \frac{u {u'}}{u^{2} + 3} = \frac{1}{t} \)