
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
Given vectors $\overrightarrow {OA}=(3, -4)$, $\overrightarrow {OB}=(6, -3)$, $\overrightarrow {OC}=(5-x, -3-y)$.  
(1) If points A, B, C can form a triangle, find the condition that x, y must satisfy;  
(2) If $\triangle ABC$ is an isosceles right triangle, and $\angle B$ is a right angle, find the values of x, y.

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