Answer:
Let "a", "b" and "с" be sides of the triangle ("с" is the longest side).
The triangle will be:
right if a² + b² = c²
аcute if a² + b² > c²
obtuse if a² + b² < c²
a.
a=3, b=4 and c=5
a² + b² = 3² + 4² = 9 + 16 = 25 and c² = 5² = 25
25 = 25 ⇒ right triangle.
b.
a=5, b=6 and c=7
a² + b² = 5² + 6² = 25 + 36 = 61 and c² = 7² = 49
61 > 49 ⇒ аcute triangle.
c.
a=8, b=9 and c=12
a² + b² = 8² + 9² = 64 + 81 = 145 and c² = 12² = 144
145 > 144 ⇒ аcute triangle.
