Find the length of PA - deductive Geometry

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chwala
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Homework Statement
see attached
Relevant Equations
Geometry
Text question is here and solution;

Geometry diagram of a circle with a tangent PT from external point P to point T on the circle and a secant from P through A and B; labels PT, PA, AB = 6, PT = 4 and the 'Try This 16' problem text.

My approach;
##BP ×AP= PT^2##
Let ##AP= x##
Therefore, ##(6+x)x=16##
##x^2+6x-16=0##
##x=2## or##x=-8##
##⇒x=2## positive value only.

I guess this may be the only approach. Cheers!