If the function f(x) = x2 - ax - 2 is strictly decreasing on (2, 3) than a lies in the interval.
Answer & explanation
Correct answer: option 2
$f(x) = x^2-ax-2$
$f'(x) = 2x-a$
$f'(x) < 0$
2x - a < 0
2x < a → for f to be strictly decreasing, f'(x) < 0
x ∈ (2, 3) → from question
2x ∈ (4, 6)
a > 6
$\Rightarrow [6, ∞)$