Question

Срочно помогите!!!!!!​

Answer 1

$\displaystyle\bf\\1)\\\\+\left \{ {{x+y=3} \atop {x-y=7}} \right. \\-------\\2x=10\\\\x=5\\\\y=3-x=3-5=-2\\\\Otvet: \ (5 \ ; -2)\\\\2)\\\\+\left \{ {{5x-6y=7} \atop {10x+6y=8}} \right.\\---------\\ 15x=15\\\\x=1\\\\6y=5x-7=5\cdot 1-7=5-7=-2\\\\y=-\frac{2}{6} =-\frac{1}{3} \\\\Otvet: \ \Big(1 \ ; \ -\frac{1}{3} \Big)$

$\displaystyle\bf\\3)\\\\\left \{ {{4x+3y=3} \atop {2x-2y=5} \ |\cdot(-2)} \right. \\\\\\+\left \{ {{4x+3y=3} \atop {-4x+4y=-10}} \right.\\ -----------\\7y=-7\\\\y=-1\\\\4x=3-3y=3-3\cdot(-1)=3+3=6\\\\x=6:4=1,5\\\\Otvet: \ (1,5 \ ; \ -1)$