设增长率为x450+450(x+1)+450(x+1)^=1638450(1+x+1+x^+2x+1)=1638x^+3x-0.64=0a=1,b=3,c=-0.64b^-4ac=11.56x=-3.2 (舍去) x=0.2即x=0.2=20%
设增长率为X450 × (1+x) × (1+x) × (1+x) = 1638X=53.83%