Step-by-step explanation:
4 ,5 ,15 cannot form a triangle
In order to form a triangle the sum of length of the the two sides should exceed the third side so here
4+5 > 15
9 > 15 ( False)
5+15> 4
20> 4 ( True)
15 + 4> 5
19> 5 (True)
Here it should all be true here so it can't form a triangle.
Hope it will help :)