`#Mon`
`\text{ Ta có:}` `{(2x+2y+xy=5),(27(x+y)+y^3+7=26x^3+27x^2+9x):}`
`<=>{((x+y)(y+2)=9),(27(x+y)+y^3+7=26x^3+27x^2+9x):}`
`<=>y^3+x^3+7+3(x+y)(x+2)(y+2)=27x^3+27x^2+9x`
`<=>y^3+x^3+8xy(x+y)+12(x+y)+6(x+y)^2=(3x+1)^3`
`<=>(x+y+2)^3=(3x+1)^3`
`=>x+y+2=3x+1`
`<=>y+1=2x`
`=>(x+2)(2x+1)=9`
`=>` \(\left[ \begin{array}{l}x=1\Rightarrow y=1\\x=-3,5\Rightarrow y=-8 \end{array} \right.\)
`Vậy` `(x;y) in {(1, 1);(-3, 5, -8)}`
