先展开方程:X*(100-x)=500100X-X^2=500X^2-100X+500=0X^2-100X+2500=2000(X-50)^2=2000=400*5X-50=±20√5X=50±20√5
x*(100-x)=500x*2-100x+500=0x*2-100x+2500=2000 (x-50)*2=2000 x-50=20√5x1=20√5+50 x2= -20√5+50