Question

Реши систему уравнений методом подстановки: {у=-3х {х-у=21​

Answer 1

$\{ {{y=-\frac{63}{4} } \atop {x=\frac{21}{4}}} \right$

Объяснение:

$\left \{ {{y=-3x} \atop {x-y=21}} \right. \\\left \{ {{y=-3x} \atop {x+3x=21}} \right\\\left \{ {{y=-3x} \atop {4x=21}} \right\\\left \{ {{y=-3x} \atop {x=\frac{21}{4} }} \right\\\left \{ {{y=-3*\frac{21}{4} } \atop {x=\frac{21}{4}}} \right\\\left \{ {{y=-\frac{63}{4} } \atop {x=\frac{21}{4}}} \right\\$