The set of values of a for which 4t−(a−4)2t+9a4 < 0 ∀ tϵ(1,2) is
Let 2t =x then f(x) = x2 - (a - 4) x +9a4
F(x) < 0. "for every x ϵ (21,22)
One of the roots of f(x) must be less than 2 and the other must be greater than 4
i.e. f(2) < 0and f(4) < 0
⇒aϵϕ