#### Answer

None.

#### Work Step by Step

Let x be the critical point. This implies f'(x)=0 or f is not differentiable.
The function f which is a linear function is differentiable at every point.
Also f'(x)= $\frac{d}{dx}(7x-2)= 7$
⇒ f'(x)≠0.
Thus f(x)=7x-2 has no critical points.