Tìm x, biết: 1) (1/3)^x - 1 = 1/243; 2) (2/3)^2.x + 3 = 8/27

bài 1 tìm x
1) (1/3)^x-1=1/243
2) (2/3)^2.x+3=8/27
3) 31/28.(28/31)^x=28/31