The parabolas defined by the equations y=-x^2-x+1 and y = x^2 + x - 3 intersect at points (a,b) and (c,d), where c >= a. What is c-a? Express your answer as a common fraction.
+36916 -x^2-x+1 = x^2 + x - 3
2x^2 + 2x-4 = 0
x^2 +x -4 = 0
(x-1)(x+2) = 0 x = 1 and -2 1 - -2 = 3
