Question

решите систему уравнений способом сложения​

Answer 1

$1.;begin{cases}5x+y=20\2x-y=1end{cases}Rightarrowbegin{cases}5x+y+2x-y=20+1\5x-y=1end{cases}Rightarrow\Rightarrowbegin{cases}7x=21\y=2x-1end{cases}Rightarrowbegin{cases}x=3\y=5end{cases}\\\2.;begin{cases}2x-3y=9\4x+3y=27end{cases}Rightarrowbegin{cases}2x-3y+4x+3y=9+27\4x+3y=27end{cases}Rightarrow\Rightarrowbegin{cases}6x=36\y=9-frac43xend{cases}Rightarrowbegin{cases}x=6\y=1end{cases}$

$3.;begin{cases}2x+3y=2\-2x+5y=-18end{cases}Rightarrowbegin{cases}2x+3y=2\-2x+5y+2x+3y=-18+2end{cases}Rightarrow\Rightarrowbegin{cases}x=2-frac32y\8y=-16end{cases}Rightarrowbegin{cases}x=5\y=-2end{cases}\\4.;begin{cases}x+4y=39\2x-y=15;;;times4end{cases}Rightarrowbegin{cases}x+4y=39\8x-4y=60end{cases}Rightarrow\Rightarrowbegin{cases}x+4y+8x-4y=39+60\y=2x-15end{cases}Rightarrowbegin{cases}x=11\y=7end{cases}$

Answer 2

https://znanija.com/task/32425970