Hey man, we’ll first of all you just need to substitute the value of a=4 and b=-1 into the equation and you’ll get your answer. Don’t worry I’ll show you an answer.
No - there is a rule that state that the sum of two sides of a triangle must be greater than the 3rd side. While 9+15 >4 and 4+15 >9 9+4 is not greater than 15 - so this triangle cannot be made.
