设第一年的折旧率为x,则第二年折旧率为x-5%,依题意得300000(1-x)[1-(x-0.05)]=1800005(1-x)[1-(x-0.05)]=35 [1-x- (x-x²-0.05+0.05x)]=35 (1-x-x+x²+0.05-0.05x)=35(x²-2.05+1.05)=3x²-2.05+1.0...