Respuesta :

you can classification triangles based on sides length

c^2 < a^2 + b^2 = acute

c^2 >  a^2 + b^2 = obtuse

c^2 =  a^2 + b^2 = right

so 

9^2 = 81

6^2 + 8^2 = 36 + 64 = 100

81<100

So the triangle is an acute triangle


Hope it helps