题目: 多项式3x2y-7x4y2-13xy3+34按字母X的降幂排列为______. 答案: 多项式3x2y-7x4y2-13xy3+34的项为,3x2y,-7x4y2,-13xy3,34;按x降幂排列为-7x4y2-13xy3+3x2y+34.