21, 28, 35 is a Pythagorean triple because the lengths found in step 2 form a Pythagorean triple.
Pythagorean Theorem: a² + b² = c²
If a² + b² is equal to c², then the set (21, 28, 35) form a Pythagorean triple
21² + 28² = 928
√928 = 30.46 ≠ c
Therefore (21, 28, 35) DOES NOT form a Pythagorean triple
