Three questions I didn't get, help please

1. Let f be a function of one variable defined for all reals. Which of the following conditions is not sufficient to guarantee that f has an inverse?

a.f is symmetric to the origin.
b.f is strictly increasing

c.f(x)=ax^3, a =/ 0

d.f is one-to-one

2.If f(x) is replaced by y=f(x-3), the graph is

a. moved 3 units right
b. moved upwards by 3 units

c. moved downward 3 units

d. moved 3 units to the left

3. A firm's cost function is given by the following equation:

C(q) = 10+ 10Q - 4Q^2 + Q^3

If average total cost (ATC) = C/Q and is given by the sum of (AVC) and (AFC). In other words, ATC(Q)= AVC(Q) + AFC(Q)

then

$\displaystyle ATC(Q) = \frac{C(Q)}{Q} =\frac{10+ 10Q - 4Q^2 + Q^3}{Q}$ $\displaystyle AVC(Q) = \frac{10Q - 4Q^2 + Q^3}{Q} = 10 -4Q + Q^2$ $\displaystyle AFC(Q) = \frac{10}{Q}$
I'm completely lost on these three questions, help please

Thank you!