Set, Relations and FunctionsPYQ Jun 23Question 1972 of 217
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If f(x):N→R\displaystyle f(x): N \to R is a function defined as f(x)=4x+3\displaystyle f(x) = 4x+3, ∀x∈N\displaystyle \forall x \in N, then f−1(x)\displaystyle f^{-1}(x) is:

Options

A4+x4\displaystyle \frac{4+x}{4}
Bx+34\displaystyle \frac{x+3}{4}
Cx−34\displaystyle \frac{x-3}{4}
Dx+44\displaystyle \frac{x+4}{4}
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Correct Answer

✅ Option c — x−34\displaystyle \frac{x-3}{4}

All Options:

  • A4+x4\displaystyle \frac{4+x}{4}
  • Bx+34\displaystyle \frac{x+3}{4}
  • Cx−34\displaystyle \frac{x-3}{4}
  • Dx+44\displaystyle \frac{x+4}{4}

Detailed Solution & Explanation

To find the inverse function f−1(x)\displaystyle f^{-1}(x), we set the function equal to y\displaystyle y:
y=4x+3y = 4x + 3
Now we solve for x\displaystyle x in terms of y\displaystyle y:
y−3=4xy - 3 = 4x
x=y−34x = \frac{y-3}{4}
Replacing the variable y\displaystyle y with x\displaystyle x to express the inverse function in terms of x\displaystyle x, we get:
f−1(x)=x−34f^{-1}(x) = \frac{x-3}{4}

Hence, **Option C** is the correct answer.

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