Question

Can someone help me please ? Thanks!

Answer 1

Use pythagorean theorem for all of them
a. 3, 4, 5
3^2+4^2?5^2
9+16?25
25=25
right 

b. 5, 6, 7
5^2+6^2=7^2
25+36=49
61>49
acute

c. 64+81=144
145>144
acute

hope this helps!

Answer 2

I will give you the general approach and you can do the calculations by yourself.

Assume 3 vertices are a,b,c

if a^2 + b^2 < c^2 ->it's obtuse

a^2 + b^2 = c^2 ->it's right

a^2 + b^2 > c^2 ->it's acute

First one is right apparently, similar combination of right triangle include 6,8,10