设宽x米,长(4+x)米.
x(4+x)=(8+x)(4+x)-x(4+x)
x^2-4x-32=0
(x-8)(x+4)=0
x1=8,x2=4
8*12=96m^2
4*8=32m^2
答:96m^2或32m^2