The parabolas defined by the equations y = x^2 + 4x + 6 and y = 2x^2 + 7x - 4 intersect at points and (a,b) and (c,d), where c >= a. What is c-a?
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c = .844
a = -11.844
c - a = .844 - ( - 11.844 ) = .844 + 11.844 ≈ 12.688