From the circle C: the square of X+the square of Y +2x-2y+ 1=0, it is (x+1) 2+(y-1) 2 =1,and the known center of the circle is (-1).

If the straight line is tangent to the circle C, the distance from the center of the circle to the straight line is equal to the radius of the circle 1, i.e.

/(-1) *1+1* (1)+b/divided by the root number 2 = 1 (the distance formula from point to straight line), the solution is b=2+/- root number 2.

Equation of straight line l: y=x+2+ radical number 2 or, y=x+2- radical number 2.

If b= 1, the linear equation is y=x+ 1, and the chord length of the intersection of a straight line l and a circle c = (12+12) = root number 2.