如图
∵A(0,2),B(1,0)∴ AB:y=-2x+2∴设CD:y=-2x+k∵BO⊥AD,AB=BD∴BO是AD垂直平分线∴AO=DO∵A(0,2)∴AO=DO=2∴D(0,-2)∴-2=0*(-2)+k解得k=-2所以CD:y=-2x-2