Suppose there is a point A on the straight line X+Y- 1=0, and the straight line Y=KX+B is perpendicular to the known straight line. Since the center of the circle is in the second quadrant, let A be the center of the circle. Then, after passing through two symmetrical points E (X 1, Y 1) on the straight line Y=KX+B, their distances to point A are both radii (i.e. root number 2).

2. Because the straight line does not pass through the origin, only one line intersects the positive semi-axis of the two axes. If a straight line equation is set, then this straight line is perpendicular to the straight line X+Y- 1=0, and because this straight line passes through the intersection of the straight line X+Y- 1=0 and the circle, it can be substituted into the straight line equation to solve it.

Added the first step, is that clear?