[PoseidonX]

ทำแบบนี้ใช่หรือเปล่าครับ


${x^2+y^2=1}$ ----- (1)
${2xy=1}$ ------(2)

(1)+(2); ${x^2+2xy+y^2 = (x+y)^2 = 2}$
${ x+y = \pm \sqrt{2} }$


(1)-(2); ${x^2-2xy+y^2 = (x-y)^2 = 0}$
${ x=y }$

ดังนั้น

${2x = \pm \sqrt{2}}$
${x = y = \pm \frac{\sqrt{2}}{2} }$