An excellent answer has been already given by Michael J., thus I am just adding couple words in regards to the computational part. Approximating the transcendental number e as 2.7182818, the following quadratic equation in its canonical form:
x2 + 8x - 2.7182818 = 0
can be easily solved using online quadratic equation solver (http://examn8.com/QuadraticEquations.aspx), having two real solutions (rounded):
Pertinent to this particular problem (as commented by Mark M.), the second solution is not applicable, thus there is only one solution x1.
Hope this may help.