3(-2x-x²y)-12x²y-(6y-9x²y+1).
＝﹣6x－3x²y－12x²y－6y＋9x²y－1
＝﹣6x－6y－6x²y－1
＝﹣6﹙x＋y﹚－6x²y－1
＝﹣6x²y－1.