Odpowiedź:
[tex]\left \{ {{3x-7=-2y\mid\cdot2} \atop {2x-3y=9 \mid\cdot(-3)}} \right. \\\\\left \{ {{6x-14=-4y} \atop {-6x+9y=-27}} \right. \\\\dodaje ~~stronami\\\\6x-14-6x+9y=-4y-27\\\\9y-14=-4y-27~~\mid+4y\\\\9y-14+4y=-4y-27+4y\\\\13y-14=-27~~\mid+14\\\\13y-14+14=-27+14\\\\13y=-13~~\mid\div13\\\\y=-1\\\\2x-3y=9~~\land y=-1\\\\2x-3\cdot(-1)=9\\\\2x+3=9 ~~\mid-3\\\\2x+3-3=9-3\\\\2x=6~~\mid \div2\\\\x=3\\\\odp. \left \{ {{y=-1} \atop {x=3}} \right. \\\\[/tex]
[tex]Spr.\\3x-7=-2y~~\land x=3~~\land y=-1\\\\3\cdot3-7=-2\cdot(-1)\\\\9-7=2\\\\2=2\\\\L=P\\\\2x-3y=9 ~~\land x=3~~\land y=-1 \\\\2\cdot3-3\cdot(-1)=9\\\\6+3=9\\\\9=9\\\\L=P[/tex]