Question

raiz 3 + x = raiz 9 - x

Answer 1

$\sqrt{3} + x = \sqrt{9} - x$
$x + x = \sqrt{9} - \sqrt{3}$
$2x = 3 - \sqrt{3}$
$x = \frac{3 - \sqrt{3} }{2}$

Answer 2

raiz{3} + x =  raiz{9} - x
coloque as incógnitas (x) na esquerda e as raízes na direita , mudando o sinal ao passar de lado:
x + x =  raiz{9} -  raiz{3}
2x = 3 -  raiz{3}
x = 3 - raiz 3 / 2

S = { x =  3 - raiz 3 / 2  }