v - 2 = K e^{4x}(v + 2) \;\Longrightarrow\; v\bigl(1 - K e^{4x}\bigr) = 2\bigl(1 + K e^{4x}\bigr) \;\Longrightarrow\; v = 2\,\frac{1 + K e^{4x}}{1 - K e^{4x}}.
Passo 8
Voltando a y, lembrando v=y-4x:
y - 4x = 2\,\frac{1 + K e^{4x}}{1 - K e^{4x}} \quad\Longrightarrow\quad y = 4x + 2\,\frac{1 + K e^{4x}}{1 - K e^{4x}}.