ax²+bx+c=0中有：x1 +x2 =-b/a x1·x2 = c/a2X²-9X+6=0中：a=2 b=-9 c=6x1 + x2 = -b/a = 9/2x1·x2 = c/a = 3(x1 - x2)² = (x1)² - 2x1·x2 + (x2)²=(x1)² + 2x1·x2 + (x2)² -...