X 2 81x 0 July 8, 2019 16 32 64 128 X 6 81x 2 0 X 4 81x 2 0 X 3 18x 2 81x 0 X 3 x 2 81x 81 0 X 3 9x 2 81x 729 0 X 2 - 81≤0 X2 − 81 = 0 81 - x ^ 2 = 0
