Помогите решить систему

Question

Помогите решить систему

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Answer 1

{х+у=3(х-у)
{х^2+у^2=90

{х+у=3х-3у
{х^2+у^2=90

{х+у-3х+3у=0
{х^2+у^2=90

{-2х+4у=0
{х^2+у^2=90

{х-2у=0
{х^2+у^2=90
х=2у
4у^2+у^2=90
5у^2=90
у^2=18
у1=-V18=-3V2
y2=3V2
x1=-6V2
x2=6V2
(-6V2;-3V2)(6V2;3V2)