∵(x+1)*30%+(100-x)*25%=40% ==>30(x+1)+25(100-x)=40 (等式两端同乘100) ==>6(x+1)+5(100-x)=8 (等式两端同除5) ==>6x+6+500-5x=8 ==>6x-5x=8-500-6 ==>x=-498 ∴此方程的解是x=-498.
