`+) x^2 + y^2 = 36`
`=> y^2 = 36 - x^2`
`+) (x + 4)^2 + y^2 = 64`
`=> (x + 4)^2 + 36 - x^2 = 64`
`=> x^2 + 2x. 4 + 4^2 + 36 - x^2 = 64`
`=> (x^2 - x^2) + 8x + 16 + 36 = 64`
`=> 8x = 64 - 36 - 16 = 12`
`=> x = 12 : 8 = 1,5`
`=> y^2 = 36 - (1,5)^2 = 36 - 2,25 = 33,75`
Vậy \(\left\{\begin{matrix}x=1,5\\y^2=33,75\end{matrix}\right.\)