Question

Решить способом подставки​

Answer 1

$x = 4 + 3y \\ 20 + 18y = - 1 \\ = > y = - \frac{21}{18} = - \frac{7}{6} = - 1 \frac{1}{6} \\ = > x = 0.5$

$3x - 4y = 5 \\ x = - 2 - 5y \\ \\ - 6 - 19y = 5 \\ y = - \frac{11}{19} \\ x = \frac{17}{19}$

Answer 2

$1. \; \left \{ {{x-3y=4} \atop {5x+3y=-1}} \right.\; \; \left \{ {{x=3y+4\qquad } \atop {5(3y+4)+3y=-1}} \right.\; \; \left \{ {{x=3y+4} \atop {18y=-21}} \right.\; \; \left \{ {{x=3y+4} \atop {y=-\frac{7}{6}}} \right. \left \{ {{x=-\frac{21}{6}+4} \atop {y=-\frac{7}{6}}} \right.\\\\\left \{ {{x=\frac{1}{2}} \atop {y=-\frac{7}{6}}} \right.\; \; \left \{ {{x=0,5} \atop {y=-1\frac{1}{6}}} \right. \; \; \; Otvet:\; (0,5\, ;\, -1\frac{1}{6})\; .$

$2.\; \; \left \{ {{3x-4y=5} \atop {x+5y=-2}} \right.\; \; \left \{ {{3(-5y-2)-4y=5} \atop {x=-5y-2}} \right.\; \; \left \{ {{-19y=11} \atop {x=-5y-2}} \right.\; \; \left \{ {{y=-\frac{11}{19}} \atop {x=\frac{55}{19}-2}} \right.\; \; \left \{ {{y=-\frac{11}{19}} \atop {x=\frac{17}{19}}} \right.\\\\Otvet:\; \; (-\frac{11}{19}\, ;\, \frac{17}{19})\; .$