2х + 5у - у в квадрате=6            2 х+у=11 пожалуйста решите функцию

     2х=11-у                                                                        yy-4y-5=0
={                                                                                       y1+y2=4
    11-y +5y-yy=6                                                               y1*y2=-5
    2x=11-y                                                                          y1+y2=5-1
={                                                                                         y1*y2=5*(-1)
    yy-4y-5=0
     x=(11-5)|2
={    
     y=5
     x=3                                x=6
={                      или              
      y=5                                y=-1