1、1200-50(x-30)x=28000 ,1200-50x^2+1500x=28000,x^2-30x+536=0 ,判别式 = (-30)^2-4*536 = -1244 < 0 ,因此无实数解.2、800-20(x-60)(x-50)=12000 ,化简得 x^2-110x+3560=0 ,判别式 = (-110)^2-4*3560 = -2140 < ...