问题 填空题 x-yx+2y=3,则代数式2(x-y)x+2y-x+2y3(x-y)的值为______. 答案 已知x-yx+2y=3,则x+2yx-y=13,则原式=2×3-13×13=6-19=589.故答案为:589.