Let, f: R→R: f(x) = x2 - 17. What is the pre-image of -1  

  1. -1, 1
  2. 2√3, -2√3
  3. -4, 4 
  4. 2, -2

Answer (Detailed Solution Below)

Option 3 : -4, 4 
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NDA 01/2025: English Subject Test
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Detailed Solution

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Concept:

If f(x) = y, we say, y is the image of x under f and x is the pre-image of y under f

 

Calculation:

Here, f: R→R: f(x) = x2 - 17

⇒f(x) = -1 

⇒ x2 - 17 = -1

⇒ x2 = 16

⇒ x = -4, 4

So, -4, 4 are the pre-images of -1.

Hence, option (3) is correct.

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