Set, Relation and FunctionHard

Question

Let f, g and h be real-valued functions defined on the interval [0, 1] by f(x) = ex2 + e- x2, g(x)= xex2 + e- x2 and h (x) = x2 ex2 + e- x2 . If a, b and c denote, respectively, the absolute maximum of f, g and h on [0, 1], then

Options

A.a = b and c≠ b
B.a = c and a ≠  b
C.a ≠  b and c ≠ b
D.a = b = c

Solution

f(x) = ex2 + e- x2 ⇒ f′(x) = 2x(ex2 + e- x2) ≥ 0 ∀ x ∈ [0, 1]
Clearly for 0 ≤ x ≤ 1        f(x)≥ g(x) ≥ h(x)
∵ f(1) = g(1) = h(1) = e + and f(1) is the greatest
∴ a = b = c = e + ⇒ a = b = c.

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