{ 2x +9y =2 ; 8x -15y =25. ⇔ { -8x -36y =2*(-4) ; 8x -15y =25. || + || ⇔
{-53y = 17; 8x -15y =25.⇔{y = -1/3 ; 8x -15*(-1/3) =25.⇔{y = -1/3 ;8x+5 =25. ⇔ { y= -1/3 ; x =5/2 .
* * * ИЛИ * * *
{ 2x +9y =2 ; 8x -15y =25.⇔ {10x +45y =2*5 ; 24x - 45y =25*3. || +|| ⇔
{ 34x =2*5 + 25*3 ; 24x - 45y =25*3.⇔{17*2x =17*5 ;8x -15y =25. ⇔
{ x = 5/2 ; 8*(5/2) - 15y =25. ⇔{ x = 5/2 ; 20 -25 =15y.⇔ {x = 5/2; y = -5/ 15.⇔
{x = 5/2; y = -1/ 3.
ответ : x =2,5 ; y = -1/3