Question:

Let \( f(x) = x^2 - 10x - 19, \, x \in \mathbb{R} \). Then the inverse image of 5, \( f^{-1}(5) = \)

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Inverse image means solving \( f(x)=k \), not finding inverse function.
Updated On: Apr 21, 2026
  • \( \{-2, -12\} \)
  • \( \{-2, 12\} \)
  • \( \{2, -12\} \)
  • \( \{2, 12\} \)
  • \( \phi \)
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The Correct Option is B

Solution and Explanation

Concept: Inverse image means solving: \[ f(x) = 5 \]

Step 1:
Set equation.
\[ x^2 - 10x - 19 = 5 \]

Step 2:
Simplify.
\[ x^2 - 10x - 24 = 0 \]

Step 3:
Factorize.
\[ x^2 - 10x - 24 = (x-12)(x+2)=0 \]

Step 4:
Solve.
\[ x = 12, -2 \] \[ f^{-1}(5)=\{-2,12\} \]
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