Question 286259
For background see the link below:

http://mathworld.wolfram.com/ObtuseTriangle.html

Let a = 7, b = 24 and c = 30.

a^2 = 49, b^2 = 624 and c^2 = 900

If the triangle is a right triangle then a^2 + b^2 = c^2 
Since 7^2 + 24^2 is not equal to 30^2 it's not a right triangle. 

Since 7^2 + 24^2 is less than 30^2 the triangle is obtuse