Answer:
x is 8
Explanation:
One of the lines is tangent to the circle while the other is a secant. In this case, we have x^2 = 4*16 which we can solve as x=8.
This is called the Power Of A Point Theorem. Here is a definition: In elementary plane geometry, the power of a point is a real number h that reflects the relative distance of a given point from a given circle. ... This equality is sometimes known as the "secant-tangent theorem", "intersecting chords theorem", or the "power-of-a-point theorem"