4.(1/3)^n=1/81
1^n=1
3^n=81
3^4=81==>n=4
3. P= 8 4/25=8×25+4/25=204/25=8,16
4l=P==>4l=8,16=l=2,04m
A patratului= L^2=L×L=2,04m×2,04m=4,1616m²
