Question 908857
a^2 + b^2 = c^2


8^2 + 16^2 = 18^2


64 + 256 = 324


320 = 324 ... this is close, but no cigar. 



Since 320 = 324 is false, this means the triangle with sides 8,16,18 is NOT a right triangle. The 3 sides a,b,c need to make a^2 + b^2 = c^2 true (c is the longest side) for a right triangle to be possible.