Given f (x) = $\frac{x^2+2x+1}{x^2-8x+12}$ Here, f(x) is a rational function of x as $\frac{x^2+2x+1}{x^2-8x+12}$ is a rational expression. ∴ f(x) assumes real values ∀ x except for the values of x for which $x^2$ – 8x + 12 = 0 i.e., (x – 6) (x – 2) = 0 ⇒ x = 6, 2 ∴ Domain of f (x) = R – {2, 6}.