1500×1.5(1-x)²=2000 (1-x)²=8/9 1-x=±√(8/9)=±2(√2)/3 x=1±2(√2)/3 即x1=(3+2√2)/3,x2=(3-2√2)/3 近似值是 x1=1.943,x2=0.0572
