To do a 90 degree clockwise rotation about the origin, we know that a point moves from ( x,y) to ( y, -x)
First we need to find the coordinates of point B
B is at ( -4, 1)
The x coordinate is -4 and the y coordinate is 1
The new location of point B will be at ( y, -x) or at ( 1, - -4) or at ( 1, +4)
