∫(x^3 - x, x, -1, 3) + ∫(1 - x^3, x, 1, 3) + ∫(1 - x, x, 1, 3) + ∫(x, x, -1, 1)
= ∫(x^3 - x, x, -1, 1) + ∫(x^3 - x, x, 1, 3) + ∫(1 - x^3, x, 1, 3) + ∫(1 - x, x, 1, 3) + ∫(x, x, -1, 1)
= 0 + ∫(x^3 - x, x, 1, 3) + ∫(1 - x^3, x, 1, 3) + ∫(1 - x, x, 1, 3) + 0
= ∫(x^3 - x + 1 - x^3 + 1 - x, x, 1, 3)
= ∫(2 - 2·x, x, 1, 3)
= [2·x - x^2](1 bis 3)
= (2·3 - 3^2) - (2·1 - 1^2)
= -3 - (1)
= - 4