If you want no values of x, it can be any positive value other than 8. If you want all values of x, the value must be 8. If you want only one value of x, it is impossible because both equations have the same slope.
The negative in the exponent makes it so there is a 1 over the problem if there was no negative. When you have a negative in the exponent, the answer will be the reciprocal (opposite) of the question with no negative. For example,
