4x² -360000+1200x-x² -x² =0
6x² -360000+1200x=0
x² +200x-60000=0
(x+100)² -70000=0
（x+100)² =70000
x1=100根号7-100 x2=-100根号7-100
4x² -360000+1200x-x² -x² =0
6x² -360000+1200x=0
x² +200x-60000=0
(x+100)² -70000=0
（x+100)² =70000
x1=100根号7-100 x2=-100根号7-100