NTA Abhyas JEE Main2020MathematicsDifferentiationPractice
If f x is a twice differentiable function such that f " x = - f x , f ' x = g x , h x = f 2 x + g 2 x and h 10 = 10 , then h 5 is equal to
Options
- A5
- B15
- C10
- D17
Correct answer
C. 10
Step-by-step solution
h ' x = 2 f ⋅ f ' + 2 g g ' = 2 f ⋅ f ' + 2 f ' f "   ( ∵ g = f ' ) = 2 f ⋅ f ' + 2 f ' - f = 0 ∴ h ' x = 0 ⇒ h x is a constant function ∴   h x = 10 ⇒   h 5 = 10