Find the maximum value of 2x3 – 24x + 107 in the interval [1, 3]. Find the maximum value of the same function in [–3, –1].

let f(x) = 2x3 – 24 x + 107


f'(x) = 6 x2 – 24 = 6(x2 – 4)


Now,


f'(x) = 0


6(x2 – 4) = 0


x2 = 4


x = ±2


We first consider the interval [1, 3].


Then, we evaluate the value of f at the critical point x = 2 [1, 3] and at the end points of the interval [1, 3].


f(2) = 2 (23)– 24 (2) + 107 = 75


f(1) = 2(1)3 – 24(1) + 107 = 85


f(3) = 2(3)3– 24 (3) + 107 = 89


Hence, the absolute maximum value of f(x) in the interval [1, 3] is 89 occurring at x = 3,


Next, we consider te interval [ – 3, – 1].


Evaluate the value of f at the critical point x = – 2 [1, 3]


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