16: D( f ) = ℝ; f is continuous there.

y-intercept: f (0) = 12; x-intercepts: f = 0 you probably can't solve.

Some help from bisection method:
f (0) = 12 > 0, f (2) = −10 < 0, f (1) = 1 > 0, hence a root between 1 and 2;
f (10) > 0, f (7) < 0, f (8) > 0, hence a root between 7 and 8;
f (−5) < 0, f (−2) > 0, f (−3) < 0, hence a root between −3 and −2.

f is not symmetric, see f = 0.
Limits at endpoints:

Interpretation as asymptotes:
No horizontal asymptote at −∞, but a chance for oblique.

So no oblique there.
No horizontal asymptote at ∞, but a chance for oblique.

So no oblique there.

Now determine monotonicity using f ′.

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