how to solve

how to solve

9x^4=100

$\begin{array}{rcll} 9\cdot x^4 &=& 100 \quad & | \quad :9 \\ x^4 &=& \frac{100}{9} \\ x^4 &=& \frac{10^2}{3^2} \\ (x^2)^2 &=& \frac{10^2}{3^2} \\ (x^2)^2 &=& \left( \frac{10}{3} \right)^2 \quad & | \quad \sqrt{} \\ x^2 &=& \frac{10}{3} \quad & | \quad \pm \sqrt{} \\ x &=& \pm\sqrt{ \frac{10}{3} } \\ x_1 &=& + 1.82574185835\\ x_2 &=& - 1.82574185835\\ \end{array}$