Example 5:  PA is tangent to the circle at point A.  Find x:

Solution:  (x + 4)(x + 4) = (x + 12)x

So x² + 8x + 16 = x² + 12x

Subtracting x² from both sides gives

8x + 16 = 12x

So 4x = 16, and we get x = 4.

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