Let f : (- , ) - \0\ R be a differentiable function such that f'(1) = a a2 f ( 1a ). Then a a(a + 1)2 -1 ( 1a ) + a2 - 2 e a is equal to
- 52 + 8
- 38 + 4
- 34 + 8
- 32 + 4
Answer
BONUS
Solution
Intended reading: the given expression is a2 f ( 1a ); put x = 1a:
f(x) = 1 + x2 -1x + 1 + 2x2 e x
required limit = a a2 f ( 1a ) = f'(1)
f'(x) = 12 -1x + 1 + x2(1 + x2) + 4x e x + 2x
f'(1) = 8 + 12 + 0 + 2 = 52 + 8
the stem as printed does not state this relation, the question was dropped
Answer: Bonus (full marks to all who attempted)