i. 22 = 4, 62 = 36, 72 = 49
But, 4 + 36 ≠ 49
∴ 22 + 62 ≠ 72
∴ 2, 6 and 7 is not a Pythagorean triplet.
ii. 92 = 81, 402 = 1600, 412 = 1681
Now, 81 + 1600 = 1681
∴ 92 + 402 = 412
∴ 9,40 and 41 is a Pythagorean triplet.
iii. 42 = 16, 72 = 49, 82 = 64
But, 16 + 49 ≠ 64
∴ 42 + 72 ≠ 82
∴ 4, 7 and 8 is not a Pythagorean triplet.