Question 180148
there is one case when a fraction can be undefined in the real numbers....that is when it looks like this a/0.....the a can be any number or mixture of numbers the part that makes it undefined is 0 in the denominator

so in this problem, it will be undefined when x+1=0.....

x+1=0 when x=-1.....therefore 15-x/x+1 will be undefined when x=-1 because it makes the denominator 0