Question

ПОЖАЛУЙСТА ПОМОГИТЕ!Решите системы {3х+у=-3 -5х+у=7
{х+5у=2 4х+7у=-5

Answer 1

$\displaystyle 1)\left \{ {{3x+y=-3} \atop {-5x+y=7}} \right. \\\\\left \{ {{y=-3-3x} \atop {-5x+y=7}} \right. \\\\-5x-3-3x=7\\\\x=-\frac{5}{4}\\ \\y=-3-3(-\frac{5}{4})\\ \\y=\frac{3}{4}\\ \\(x,y)=(-\frac{5}{4},\frac{3}{4})\\ \\2)\left \{ {{x+5y=2} \atop {4x+7y=-5}} \right. \\\\\left \{ {{x=2-5y} \atop {4x+7y=-5}} \right.\\ \\4(2-5y)+7y=-5\\y=1\\x=2-5*1\\x=-3\\(x,y)=(-3,1)$