Let f(x) = ax + b

We need to find the derivative of f(x) i.e. f’(x)

We know that,

…(i)

f(x) = ax + b

f(x + h) = a(x + h) + b

= ax + ah + b

Putting values in (i), we get

f’(x) = a

Hence, f’(x) = a