
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
In the rectangular coordinate system, a coordinate system is established with the origin as the pole and the positive semi-axis of the x-axis as the polar axis. Given the curve C: ρsin²θ=2acosθ (a>0), and the parametric equation of the line L passing through the point P(-2, -4) is: $$\begin{cases} x=-2+ \frac { \sqrt {2}}{2}t \\ y=-4+ \frac { \sqrt {2}}{2}t\end{cases}$$, where L intersects with C at points M and N.
(I) Write the ordinary equations of curve C and line L.
(II) If |PM|, |MN|, |PN| form a geometric sequence, find the value of a.

Present the answer in LaTex format: \boxed{Your answer}
user