{x-y=0 {x+y+z=4 {x+2y+3z=9

z pierwszego x=y czyli {y+y+z=4 {y+2y+3z=9 2y+z=4 3y+3z=9 //3 2y+z=4 y+z=3 odejmujemy stronami y=1 z=2 x=1

{x-y=0 {x+y+z=4 {x+2y+3z=9 {x = y podstawiamy {x + x + z = 4 {x + 2x + 3z = 9 {2x + z = 4 {3x + 3z = 9 /:3 {x + z = 3 {2x + z = 4 {x = 3 - z {2 (3 - z) + z = 4 6 - 2z + z = 4 -z = 4 - 6 -z = -2 z = 2 x = 3 - 2 x = 1 {x = 1 {y = 1 {z = 2