Can you solve #9 and #10 as well as explain to me what this question means and how to solve it ? Thanks.

9. Find the equation of a circle with center (1, -1) and that passes through the origin. a. (x-1) +(+1) -2 b. (x + 1) + (y- 1)'=2 c. (x - 1)2 + () + 1)2 = 12 d. ( x -1)2 + ( y +1)2 = 0 e. (x +1)2 + (y + 1)2=2 f. (x - 1)2 + (1 + 1)2 =-2 10. Find the equation of a circle with center (2, 1) that is tangent to the x-axis. a. (x -2)+ (1- 1)2 +1=0 b. (x -2)' + (1- 1)2-1=0 c. (x - 2)2 + (y - 1)2 = 2 d. (x -2)2 + (1- 1)2 e. (x- 2)2 + (1-1)2=3 f. (x - 2)2 + (1 -1)2 - 4=0