Question

x + y+ z = 7

x + y + u = 11

x + z + u = 15

y + z + u = 3

Решить систему уравнений

Answer 1

$x+y+z=7\ x+y+u=11\ x+z+u=15\ y+z+u=3\ \ x+y=7-z\ 7-z+u=11\ u-z=4\ u=4+z\ \ x+z+4+z=15\ y+z+4+z=3\ \ x+2z=11\ y+2z=-1$
$2z=11-x\ 2z=-1-y\ 11-x=-1-y\ y-x=-12\ y=x-12\ u=4+z\ \2x+z=19\ 2z+x=11\ \x=frac{19-z}{2}\ 3z+19=22\ z=1\ x=9\ u=5\ y=-3$