# Finding the real root of the polynomial $2x^3-3x^2+2$

I want to get exactly roots of this equation...

$2x^3-3x^2+2 = 0$

I try to solve it but can not find the solution. wolframealpha just give me aproximation..

I know the real root is $-1< root <-1/2$.

• if there is just one real root you can write it using radicals with Cardano's method en.wikipedia.org/wiki/Cubic_function#Cardano.27s_method May 23 '15 at 23:10
• WolframAlpha actually gives $x\cong -0.67755$. May 23 '15 at 23:11
• There are only three methods which i can state : Cubic root formula, Cardano's method (David's answer) and Newton's method...Can't arrive at anything else. The closest i have got to is $\Rightarrow (x-1)^2 (2x+1) + 1 = 0$ Jun 18 '15 at 5:43

$\left\{\frac{1}{2} \left(1-\frac{1}{\sqrt{3-2 \sqrt{2}}}-\sqrt{3-2 \sqrt{2}}\right),\frac{1}{2}+\frac{1}{4} \sqrt{3-2 \sqrt{2}} \left(1-i \sqrt{3}\right)+\frac{1+i \sqrt{3}}{4 \sqrt{3-2 \sqrt{2}}},\frac{1}{2}+\frac{1-i \sqrt{3}}{4 \sqrt{3-2 \sqrt{2}}}+\frac{1}{4} \sqrt{3-2 \sqrt{2}} \left(1+i \sqrt{3}\right)\right\}$
The first root is real, and has a decimal approximation of $-0.677651...$.