Question

ME AJUDEMMM,NÃO CHEGOO A UM RESULTADO
{y=2x
{4y²=2xy+4

Answer 1

4.(2x)² = 2x .2x + 4

4.4x² - 4x² = 4

12x² = 4

x² = 4/12

x² = 1/3

x = -1/√3 = - √3/3
ou
x = 1/√3 = √3/3

y = 2.√3/3
ou = -2√3/3

Answer 2

$\Bmatrix y=2x\\4y^2=2xy+4\end$

substituindo na segunda equação 
2x=y

$4y^2=yy+4\\\\4y^2=y^2+4\\\\ 4y^2-y^2=4\\\\3y^2=4\\\\y^2= \frac{4}{3} \\\\y=\pm \sqrt{\frac{4}{3} }\\\\y= \pm \frac{2}{\sqrt{3}}$


logo:
$2x=y\\\\x= \frac{1}{2}*y \\\\\ x= \frac{1}{2}* \pm \frac{2}{\sqrt{3}}\\\\ x= \pm\frac{1}{\sqrt{3}}$