Compute the distance between the two foci of the ellipse $x^2 + 4y^2 = 9.$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Compute the distance between the two foci of the ellipse $x^2 + 4y^2 = 9.$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
3\sqrt3
Compute the distance between the two foci of the ellipse $x^2 + 4y^2 = 9.$
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