(x-1)^2/3=25

$${\frac{{\left({\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}^{{\mathtt{2}}}}{{\mathtt{3}}}} = {\mathtt{25}}$$

Times both sides by 3

$${\left({\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}^{{\mathtt{2}}} = {\mathtt{75}}$$

Square root both sides

$${\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{1}} = {\sqrt{{\mathtt{75}}}}$$

$${\mathtt{x}} = {\sqrt{{\mathtt{75}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}$$

$${\mathtt{x}} = {\sqrt{{\mathtt{75}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}} \Rightarrow {\mathtt{x}} = {\mathtt{9.660\: \!254\: \!037\: \!844\: \!386\: \!5}}$$