voorbeelden stelsels oplossen

 Opgave 1 $\cases{2x+3y=12\cr3x+7y=8}$ $\cases{6x+9y=36\cr6x+14y=16}$ Trek (1) van (2) af: $5y=-20$ $\cases{y=-4\cr x=12}$ Opgave 2 $\cases{2x+3y=12\cr y=2x+4}$ $\cases{2x+3(2x+4)=12\cr y=2x+4}$ $\cases{2x+6x+12=12\cr y=2x+4}$ $\cases{8x=0\cr y=2x+4}$ $\cases{x=0\cr y=4}$ Opgave 3 $\cases{y=x^2-4x\cr y=2x-4}$ $x^2-4x=2x-4$ $x^2-6x+4=0$ $(x-3)^2-9+4=0$ $(x-3)^2-5=0$ $(x-3)^2=5$ $x-3=-\sqrt 5\vee x-3=\sqrt 5$ $x=3-\sqrt 5\vee x=3+\sqrt 5$ $\cases{x=3-\sqrt 5\cr y=2-2\sqrt 5}\vee \cases{x=3+\sqrt 5\cr y=2+2\sqrt 5}$