I'm trying to find X P( x, -2/7)

$\displaystyle x^2+ -2/7=1$ then I get

$\displaystyle x^2+ (-2/7)^2=1$

Than I get $\displaystyle x^2=1-4/49= $ $\displaystyle x^2= \frac{49} {49}- \frac{4}{49}=\frac{45} {49}$ Then you get $\displaystyle x=\sqrt \frac{45} {49}$The answer is suppose to be $\displaystyle x=+ or -\sqrt{5}$.

How do you get $\displaystyle x= + - \sqrt{5}$

Thanks

Jason