extraneous roots with logs?

Hi, I have these four questions that I cannot seem to understand what they are asking me to solve. I do not know how to begin the question.

The questions are as followed:

3. Solve. Identify and reject any extraneous roots. Check your solutions using graphing technology.

a) $\displaystyle log x + log (x-4) = 1$

b) $\displaystyle log x^3 - log 2 = log (2x^2)$

c) $\displaystyle log (v-1) = 2 + log (v-16)$

d) $\displaystyle 1 + log y = log (y+9)$

How would I do these? My teacher only showed us the way to solve these when they are adding? (Worried)