$1,5x^2-1,5y^2-18y=1,2x^2-0,3y^2-18y=0$
`<=>`$1,5x^2-1,5y^2-18y-1,2x^2+0,3y^2+18y=0$
`<=>`$0,3x^2-1,2y^2=0$
`<=>`$0,3(x^2-4y^2)=0$
`<=>`$x^2-4y^2=0$
`<=>`$x^2=4y^2$
Ta có:
$1,5x^2-1,5y^2-18y=0$
`<=>`$1,5.4y^2-1,5y^2-18y=0$
`<=>`$6y^2-1,5y^2-18y=0$
`<=>`$4,5y^2-18y=0$
`<=>`$4,5y(y-4)=0$
`<=>[(4.5y=0),(y-4=0):}`
`<=>[(y=0(loại)),(y=4(t//m)):}`
`=>x^2=4.4^2=64`
`=>[(x=8(t//m)),(x=-8(loại)):}`
Vậy $x=8; y=4$
