Every autonomous ­first-order equation dy/dx = f (y) is separable. Find explicit solutions y1(x), y₂(x), y₃(x), and y₄(x) of the differential equation dy/dx = y - y³ that satisfy, in turn, the initial conditions y₁(0) = 2, y₂(0) = ½, y₃(0) = -1 and y₄(0) = -2. Use a graphing utility to plot the graphs of each solution. Compare these graphs with those predicted in Problem 19 of Exercises‑2.1. Give the exact interval of defi­nition for each solution.