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The function f(x) is a polynomial and hence it is defined for all real numbers. Its second derivative is given by f''(x) = 5x + 3x^2.
Find the intervals over which the function f(x) is concave up.
A) -3,1 and 2
B) -3 and 1
C) -3 and 1.2
D) -3,2
E) -3 and 2
F) None of the above