[tex]-x^{2} +6x=8\\x^{2} -6x+8=0\\ (x-2)(x-4)=0\\D=6^{2} -8*4=4=2^{2} \\x_{1} =\frac{6+2}{2} =4\\x_{2} =\frac{6-2}{2} =2\\[/tex]

Ответ:{4,2}