Question

допоможіть будь ласка з алгеброю дам 40 баллiв

Answer 1

$\displaystyle\bf\\1)\\\\-\left \{ {{2x+y=17} \atop {3x+y=22}} \right.\\ ---------\\-x=-5\\\\x=5\\\\y=17-2x=17-2\cdot 5=17-10=7\\\\Otvet \ : \ (5 \ ; \ 7)\\\\\\2)\\\\\left \{ {{x+y=13} \atop {y-x=3}} \right.\\\\\\+\left \{ {{x+y=13} \atop {-x+y=3}} \right. \\---------\\2y=16\\\\y=8\\\\x=13-y=13-8=5\\\\Otvet \ : \ (5 \ ; \ 8)\\\\3)\\\\\left \{ {{x+2y=30} \atop {2x+y=30}|\cdot(-2)} \right. \\\\\\+\left \{ {x+2{y=30} \atop {-4x-2y=-60}} \right.\\ -----------\\-3x=-30$

$\displaystyle\bf\\x=10\\\\y=30-2x=30-2\cdot 10=30-20=10\\\\Otvet \ : \ (10 \ ; \ 10)$