1﹚2x²－6x＋7＝2﹙x²－3x＋7/2﹚＝2[x²－3x＋﹙3/2﹚²－﹙3/2﹚²＋7/2] ＝2﹙x－3/2﹚²＋5/2≥5/2∴2x²－6x＋7＞02﹚ 2x²＋x－3＝2﹙x²＋1/2 x－3/2﹚＝2﹙x＋1/4﹚&...