[tex]x^2-10x+25=35\\\\x^2-2\cdot5\cdot x + 5^2=35\ \ \ |\text{use:}\ (a-b)^2=a^2-2ab+b^2\\\\(x-5)^2=35\to x-5=\pm\sqrt{35}\ \ \ |+5\\\\\boxed{x=5-\sqrt{35}\ \vee\ x=5+\sqrt{35}}[/tex]
[tex]\text{other method}\\\\x^2-10x+25=35\\\\x^2-5x-5x+25=35\\\\x(x-5)-5(x-5)=35\\\\(x-5)(x-5)=35\\\\(x-5)^2=35\\.....[/tex]
