
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 an ellipse $\dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1$ with its left and right foci being $F_{1}$ and $F_{2}$ respectively, a perpendicular line to the x-axis through the left focus $F_{1}(-2,0)$ intersects the ellipse at points $P$ and $Q$. The line $PF_{2}$ intersects the y-axis at $E(0, \dfrac {3}{2})$. $A$ and $B$ are points on the ellipse located on either side of $PQ$.
- (I) Find the eccentricity $e$ and the standard equation of the ellipse;
- (II) When $\angle APQ=\angle BPQ$, is the slope $K_{AB}$ of line $AB$ a constant value? If so, find this constant value; if not, explain why.

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