15: D( f ) = (−∞,0) ∪ (0,∞); f is continuous there.

y-intercept: f (0) not possible; x-intercepts: f = 0 gives x = 1.
f is not symmetric, see f = 0.
Limits at endpoints:

Interpretation as asymptotes:
Horizontal asymptote y = −π/4 at −∞.
Not a vertical asymptote at x = 0.
Horizontal asymptote y = π/4 at ∞.

Now determine monotonicity using f ′.

Next hint
Answer