X 2 81y 2 July 8, 2019 16 32 64 128 X 2 81y 2 factored X 2 18xy 81y 2 Factorise x 2 81y 2 X 2 6xy 81y 2 X 4 9x 2y 2 81y 4 X 4 18x 2y 2 81y 4 X 2 - 81≤0 Y = - x ^ 2 + 81