Answer:
C
Step-by-step explanation:
In a Pythagorean triple the square on the longest side is equal to the sum of the squares on the other 2 sides.
A
longest side = 10 ⇒ 10² = 100
6² + 8² = 36 + 64 = 100
A is a Pythagorean triple
B
longest side = 17 ⇒ 17² = 289
8² + 15² = 64 + 225 = 289
B is a Pythagorean triple
C
longest side = 9 ⇒ 9² = 81
5² + 8² = 25 + 64 = 89
89 ≠ 81
C is not a Pythagorean triple
D
longest side = 13 ⇒ 13² = 169
5² + 12² = 25 + 144 = 169
D is a Pythagorean triple
