Correct Answer - Option 3 : 168x

-8
**Concept:**

\(\rm \frac{\mathrm{d} (x^n)}{\mathrm{d} x} = nx^{n - 1}\)

__Calculation:__

Given function f(x) = 4x-6

Now; f'(x) = \(\rm \frac{\mathrm{d} (4x^{-6})}{\mathrm{d} x}\)

= 4 × (-6)x^{(-6 - 1)}

f'(x)= -24x^{-7}

Again; differentiation with respect to x

f"(x) = -24 × (-7)x^{(-7 - 1)}

= 168x^{-8}

**∴ The required value is **168x-8**.**