X^0,5 + X = 15

$x^{0,5} +x = 15 \ \ \ |-x \\ \sqrt{x} = 15-x \ \ \ | \ ^2 \\ x = 225 -30x+x^2 \ \ \ |-x \\ 0=x^2-31x+225 \\ \\ \\ \underrightarrow{Mitternachtsformel} \ \ \ \ x_{1/2} = {31 \pm \sqrt{31^2-4 \cdot1 \cdot 225} \over 2} ={31 \pm \sqrt{61} \over 2}$