Question

Решите систему уравнений
{х+у=4 { 3х-5у=0
{3х+у=0 {3х+8у=-7

Answer 1

$begin{cases}x+y=4,\ 3x+y=0;end{cases}Rightarrow begin{cases}y=4-x,\ 3x+4-x=0;end{cases}Rightarrow begin{cases}y=4-x,\ 2x=-4;end{cases}Rightarrow\ Rightarrowbegin{cases}y=6,\ x=-2.end{cases}$

$begin{cases}3x-5y=0,\3x+8y=-7;end{cases}Rightarrowbegin{cases}3x-5y=0,\8y-(-5y)=-7;end{cases}Rightarrowbegin{cases}x=frac{5}{3}y,\13y=-7;end{cases}Rightarrow\ Rightarrowbegin{cases}x=-frac{35}{39},\y=-frac{7}{13}.end{cases}$