9514 1404 393
Answer:
{-5.2555, 1.1278 ± 1.2579i}
Explanation:
Descarte's rule of signs tells you there are 0 or 2 positive real roots and 1 negative real root. A graph shows you the negative roots is irrational, and the positive roots are complex.
There are formulas for solving equations of this sort. The method you use will depend on whether you need an exact result or just a numerical approximation. Exact results can be obtained in terms of radicals or in terms of trig functions.
The first attachment is from a freely available solver. It gives 4 decimal places, which is sufficient for many purposes.
The second attachment is the graph, along with the quadratic that results from dividing f(x) by the factor that gives the real root. While the values shown on the graph are to 3 decimal places, the calculator can be used to find them to greater precision. (We have used Newton's Method iteration to find the real root to 12 significant figures.)