不论x为何实数,多项式3x²-5x-1的值总大于2x²-4x-7的值_数学解答

不论x为何实数,多项式3x²-5x-1的值总大于2x²-4x-7的值

人气：437 ℃　时间：2019-08-18 02:09:42

解答

(3x²-5x-1)-(2x²-4x-7)=3x²-5x-1-2x²+4x+7=x²-x+6=(x²-x+1/4)+6-(1/4)=(x-1/2)²+23/4∵(x-1/2)²≥0∴(3x²-5x-1)-(2x²-4x-7)=(x-1/2)²+23/4＞0即：(3x²...