3 ms·
Also (x+1)(x-1) = xx -1 helps if you know the squares 1x3 = 2x2-1, 2x4 = 3x3-1, 3x5 = 4x4-1, 4x6 = 5x5-1, 5x7 = 6x6-1, 6x8 = 7x7-1, 7x9 = 8x8-1, ...
by jmlundberg 6y ago
Also (x+1)(x-1) = xx -1 helps if you know the squares
1x3 = 2x2-1,
2x4 = 3x3-1,
3x5 = 4x4-1,
4x6 = 5x5-1,
5x7 = 6x6-1,
6x8 = 7x7-1,
7x9 = 8x8-1,
...