In parts (a) and (b) sketch isoclines f (x, y) = c for the given differential equation using the indicated values of c. Construct a direction ­field over a grid by carefully drawing lineal elements with the appropriate slope at chosen points on each isocline. In each case, use this rough direction fi­eld to sketch an approximate solution curve for the IVP consisting of the DE and the initial condition y(0) = 1.

(a) dy/dx = x + y; c an integer satisfying -5 ≤ c ≤ 5

(b) dy/dx = x² + y²; c = 1/4, c = 1, c = 9/4, c = 4