6x@sup{4}-42x@sup{3}y-108x@sup{2}y@ sup{2}

point a is the center of the circle that passes through points e, f, and g and the center of the circle that passes through points x, y, and z.

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)