Answer
$(1,4),(-1,-4),(2\sqrt 2,\sqrt 2),(-2\sqrt 2,-\sqrt 2)$
Work Step by Step
1. From the 2nd equation, we get $y=\frac{4}{x}$
2. Use the above in the 1st equation, we have $2x^2+(\frac{4}{x})^2=18$ or $x^4-9x^2+8=0$
3. Factor to get $(x^2-1)(x^2-8)=0$, thus $x=\pm1, \pm2\sqrt 2$
4. Use the above with the 2nd equation to get the solutions $(1,4),(-1,-4),(2\sqrt 2,\sqrt 2),(-2\sqrt 2,-\sqrt 2)$
