x+81x^(-1)=18
x+81/x=18
x^2+81=18x
x^2-18x+81=0
D=b^2-4ac=0
x=-b/2a=9
х+81=18
х+81*1/х=18
х+81/х=18
(х^2+81)/х=18
х^2+81=18х
х^2-18х+81=0
х1=х2=9
x+81x^(-1)=18
x+81/x=18
x^2+81=18x
x^2-18x+81=0
D=b^2-4ac=0
x=-b/2a=9
х+81=18
х+81*1/х=18
х+81/х=18
(х^2+81)/х=18
х^2+81=18х
х^2-18х+81=0
х1=х2=9