[5(1+x)—1]×(1+x)=4.368，(5X+4)(X+1)=4.368，5X^2+9X+4=4.368，X^2+1.8X=0.0736，(X+0.9)^2=0.8836，X+0.9=±0.94，X1=0.04，X2=-1.84。
