As shown in the figure, in the plane rectangular coordinate system, the straight line L: y = - 2x-8 intersects with the x-axis and y-axis respectively at two points a and B. the point P (0, K) is a moving point on the negative half axis of the y-axis. Take P as the center of the circle and 3 as the radius to make ⊙ P Q: when what is the value of K, ⊙ P is tangent to the line L

As shown in the figure, in the plane rectangular coordinate system, the straight line L: y = - 2x-8 intersects with the x-axis and y-axis respectively at two points a and B. the point P (0, K) is a moving point on the negative half axis of the y-axis. Take P as the center of the circle and 3 as the radius to make ⊙ P Q: when what is the value of K, ⊙ P is tangent to the line L

L:y=-2x-8
The result is: 2x + y + 8 = 0
∵ P (0, K), radius r = 3
∴d=|k+8|/√5=r=3
∴|k+8|=3√5
∴k+8=±3√5
∵k<0
∴k=-8±3√5