Question

Способом алгебраического сложения решить систему уравнений {8x - 3y = −4,
3x + y = 7.​

Answer 1

$\displaystyle \left \{ {{8x-3y=-4} \atop {3x+y=7}} \right. \\\\(8x-3y)+3(3x+y)=-4+3*7\\17x=17\\x=1\\8*1-3y=-4\\y=4\\(x,y)=(1,4)$

Answer 2

$\displaystyle\bf\\\left \{ {{8x-3y=-4} \atop {3x+y=7} \ |\cdot 3} \right. \\\\\\+\left \{ {{8x-3y=-4} \atop {9x+3y=21}} \right. \\----------\\17x=17\\\\x=1\\\\y=7-3x=7-3\cdot 1=7-3=4\\\\Otvet \ : \ \Big(1 \ ;\ 4\Big)$