Answer: A problem is said to be intractable if there is no efficient algorithm to solve it.
Intractable problems are common. We need to discuss how we approach it when we actually encounter it.
Explanation:
How many colours do you need to colour a graph such that no adjacent vertices are of the same colour showed in the image below?
Conclusion : Provided the graph with a large number of vertices, we see that we are again faced with resorting to a systematic tracing of all paths, comparison of the neighbour's colours, backtracking, etc resulting in exponential time complexity once again.