Х2/5-2х/3=х-5/6 "/" - дробная черта "х2" - икс во второй степени

х2/5-2х/3=х-5/6
(6x2 - 20x - 5(x-5))/30=0
6x2 - 20x - 5x + 25=0
6x2 - 25x + 25 = 0
D = 625 - 600 = 25
x1 = (25 - 5)/ 6*2 = 20/12= 1целая 2/3
x2 = (25+5)/ 12 = 30/12= 2,5