As,

To calculate dy/dx we can use quotient rule.

From quotient rule we know that :

∴

We know that,

⇒

∵ x – a is a factor of xⁿ–aⁿ, we can write:

xⁿ–aⁿ = (x–a)(x^n–1+ax^n–2+a²x^n–3+…+a^n–1)

⇒

⇒

⇒

∴

⇒

Clearly form above solution we can say that option (d) is the only correct answer.