Question

A triangle has sides of lengths 12, 14, and 19. Is it a right triangle? Explain.

Answer 1

A^2 + b^2 = c^2 
C should equal to the longer side, which would be 19. 
Plug in other two numbers for A and B. 
12^2 + 14^2 = 19^2 
Now see if it's correct. If it is, then it's a right triangle, if it's not then it isn't a right triangle. 
144 + 196 = 361 
340 = 361 
It's not a right triangle.