
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
A residential area plans to build a rectangular green space. Let the length of the rectangle be $x$ meters and the width be $y$ meters ($x > y$).
(1) If 18 meters of construction material is used to build the frame of the green space (i.e., the perimeter), find the functional relationship between $y$ and $x$ and write the range of values for $x$.
(2) According to the planning requirements of the residential area, the area of the rectangular green space must be 18 square meters. Under the condition of (1), how many meters are the length and width of the rectangle?
(3) Someone suggests changing the area of the rectangular green space to 21 square meters. Is this suggestion reasonable? Explain your reasoning.

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