Question 479127
{{{system(x^2+y^2=13,2x-3y=0)}}}
from the second equation {{{-3y=-2x}}}, or {{{y=2x/3}}}
Substitute {{{y=2x/3}}} into the first equation 
{{{x^2+(2x/3)^2=13}}}
{{{x^2+4x^2/9=13}}} 
{{{13x^2/9=13}}} multiply by 9
{{{13x^2=117}}} divide by 13
{{{x^2=9}}}
{{{x[1]=3}}}, {{{x[2]=-3}}}
substitute into {{{y=2x/3}}}
{{{y[1]=2*3/3=2}}}, {{{y[2]=2*(-3)/3=-2}}}
Answer (3,2) and (-3,-2)