We need to find derivative of f(x) = – x

Derivative of a function f(x) is given by –

f’(x) = {where h is a very small positive number}

∴ derivative of f(x) = – xis given as –

f’(x) =

⇒ f’(x) =

⇒ f’(x) =

⇒ f’(x) =

∴ f’(x) = – 1

Hence,

Derivative of f(x) = – x = – 1