Question

СРОЧНО 60 БАЛЛОВ!!!! 3,4

Answer 1

$\displaystyle\bf\\\left \{ {{x-3y=7} \atop {2x-3y=-3}} \right. \\\\\\\left \{ {{x=3y+7} \atop {2\cdot(3y+7)-3y=-3}} \right. \\\\\\\left \{ {{x=3y+7} \atop {6y+14-3y=-3}} \right.\\\\\\\left \{ {{x=3y+7} \atop {3y=-3-14}} \right. \\\\\\\left \{ {{x=3y+7} \atop {3y=-17}} \right. \\\\\\\left \{ {{x=3\cdot\Big(-\dfrac{17}{3} \Big)+7} \atop {y=-5\dfrac{2}{3} }} \right. \\\\\\\left \{ {{x=-17+7} \atop {y=-5\dfrac{2}{3} }} \right. \\\\\\\left \{ {{x=-10} \atop {y=-5\dfrac{2}{3} }} \right.$

$\displaystyle\bf\\Otvet \ : \ \Big(-10 \ ; \ -5\frac{2}{3} \Big)\\\\2)\\\\\left \{ {{2x+9y=-1 \ |\cdot(-4)} \atop {7x+36y=-8}} \right.\\\\\\+\left \{ {{-8x-36y=4} \atop {7x+36y=-8}} \right. \\----------\\-x=-4\\\\x=4\\\\9y=-1-2x=-1-2\cdot4=-1-8=-9\\\\y=-9:9=-1\\\\\\Otvet \ : \ (4 \ ; \ -1)$