solve cubic with no rational zeros

biochem850

1. The problem statement, all variables and given/known data

x^3-8x+10=0

2. Relevant equations



3. The attempt at a solution

By dividing by x-1 (1 is a factor of the solution), I got (x-1)(x²+x-7)+3+10=0

which equals x^3-8x+20=0

I think the solution would be imaginary but I used a graphing calculator and there is one solution but I don't know how to calculate it.

Mark44

What is the complete problem statement?
x - 1 is NOT a factor of x^3 - 8x + 10.
We can't help you if we don't know what it is that you're supposed to do. That's where the complete problem statement would be useful information.

LCKurtz

Unless you know how to solve a cubic by radicals, you won't be finding the exact answer for the real root. Maple gives it as:

-(1/3)*(135+3*sqrt(489))^(1/3) - 8/(135+3*sqrt(489))^(1/3)

and a decimal approximation to that is -3.318628218.