若多项式(2mx-x+3x+1)-(5x-4y+3x)的结果与x取值无关时,求3m-[（2m-5)5m+3m]的值.详细点!

(2mx - x + 3x + 1) - (5x - 4y + 3x) = 2mx - x + 3x + 1 - 5x + 4y - 3x = (2m - 1 - 5)x + 4y + 1 因为与x无关,所以有 2m - 1 - 5 = 0 即m = 3 3m - [(2m - 5) × 5m + 3m] = 3m - 10m + 25m - 3m = 3m + 28m - 10m = m(3 + 28m - 10m) 将m = 3代入得 = 3(3 + 28 × 3 - 10 × 3) = 3 × (-3) = -9