Question

9^(x-3)+9^(x-2)+9^(x-1)>511

Answer 1

9^(x-3)(1+9+81)>511
91*9^(x-3)>511
9^(x-3)>511/91
9^(x-3)>73/13
3^(2x-6)>73/13
2x-6>log(3)73/13
2x>6+log(3)73/13
x>3+0,5log(3)73/13

Answer 2

9^(x-3)(1-9+81)>511