f(x) = x^4 - 5·x^2 + 4 = 0 --> x = ±1 ∨ x = ±2
F(x) = 1/5·x^5 - 5/3·x^3 + 4·x
∫ (0 bis 1) f(x) dx = F(1) - F(0) = 38/15 - 0 = 38/15
∫ (1 bis 2) f(x) dx = F(2) - F(1) = 16/15 - 38/15 = - 22/15
∫ (2 bis 4) f(x) dx = F(4) - F(2) = 1712/15 - 16/15 = 1696/15
A = 38/15 + 22/15 + 1696/15 = 1756/15 = 117.1
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