1.
Let ff be a differentiable function with lim⁡x→∞f(x)=0\lim_{x\to\infty} f(x) = 0. If y′+yf′(x)−f(x)f′(x)=0y' + y f'(x) - f(x)f'(x) = 0, lim⁡x→∞y(x)=0\lim_{x\to\infty} y(x) = 0, then