`{(2x(y+2)-4y=-8),(x-7y=37):}`

Ta có: `x-7y=37=>x=37+7y`

Thay `x=37+7y` vào `2x(y+2)-4y=-8`, ta có:

`2(37+7y)(y+2)-4y=-8`

`2(37y+74+7y^2+14y)-4y=-8`

`2(7y^2+51y+74)-4y=-8`

`14y^2+102y+148-4y+8=0`

`14y^2+98y+156=0`

`Δ'=49^2-14·156=217>0`

`=>` pt có `2` nghiệm pb

`y_1=(-b'+\sqrt{Δ'})/a=(-49+\sqrt{217})/14`

`y_2=(-b'-\sqrt{Δ'})/a=(-49-\sqrt{217})/14`

Với `y=(-49+\sqrt{217})/14`, ta có:

`x=37+7(-49+\sqrt{217})/14=37+(-49+\sqrt{217})/2=(74-49+\sqrt{217})/2=(25+\sqrt{217})/2`

Với `y=(-49-\sqrt{217})/14`, ta có:

`x=37+7(-49-\sqrt{217})/14=37+(-49-\sqrt{217})/2=(74-49-\sqrt{217})/2=(25-\sqrt{217})/2`

Vậy `(x;y)={((25+\sqrt{217})/2;(-49+\sqrt{217})/14);((25-\sqrt{217})/2;(-49-\sqrt{217})/14)}`