मान लीजिए सभी x, y ϵ R के लिए f(x + y) = f(x) f(y) और f(2) = 4 है, जहाँ f(x) निरंतर फलन है। तो f' (2) किसके बराबर है?

  1. 2 ln 2
  2. 4 ln 2
  3. ln 8
  4. 2 ln 3

Answer (Detailed Solution Below)

Option 2 : 4 ln 2
Free
NDA 01/2025: English Subject Test
30 Qs. 120 Marks 30 Mins

Detailed Solution

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संकल्पना:

गणना:

दिया गया है कि  f (2) = 4 और f (x + y) = f(x) f(y) 

 x = 1, y = 1 रखने पर 

f(2) = f(1) f(1) = 4

f(1) = f(1) = 2

अर्थात् f(1) = 21

x = 1, और y = 2 रखने पर 

f (3) = f(1) f(2) = 2 × 4 = 23

∴ f(x) = 2x

⇒ f’(x) = 2x ln 2

∴ f’(2) = 22 ln 2 = 4 ln 2

अतः विकल्प (2) सही है।    

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