﹙2x+3y﹚-﹙2x+y﹚﹙2x-y﹚,=4x+12xy+9y-(4x-y) =4x+12xy+9y-4x+y =12xy+10y =12×1/3×(-1/2)+10×(-1/2) =-2+2.5 =0.5