The equation is undefined;
If we simplified the equation, we get:
x + 6 = x
6 = 0
Of course, we know:
6 ≠ 0
So, we say the function is undefined;
The function will be undefined when the value of y or f(x) cannot be rearranged and solve to give a value of x;
The function will have a vertical asymptote at this value of y or f(x);
Similarly, a function will be undefined when a value of x is substituted and results in an equation similar to 6 = 0, i.e. one that we know is most definitely false/impossible;
In this case, the function will have a horizontal asymptote at such a value of x.
