题目

（1）2x²-3x-6=0 (2) x² +4x+2=0 (3) 2x²-5x+2=0 能解答出来的必当重谢!

提问时间：2021-02-15

答案

（1）2x² - 3x - 6 = 0
x² - 3x/2 - 3 = 0
x² - 3x/2 + 9/16 - 3 - 9/16 = 0
(x - 3/4)² = 57/16
x - 3/4 = ± √57 / 4
x = (3 ± √57) / 4
(2) x² +4x+2=0
x² + 4x + 4 - 4 + 2 = 0
(x + 2)² = 2
x + 2 = ± √2
x = -2 ± √2
(3) 2x²-5x+2=0
x² - 5x/2 + 1 = 0
x² - 5x/2 + 25/16 - 25/16 + 1 = 0
(x - 5/4)² = 9/16
x - 5/4 = ±3/4
x = (5±3)/4