Question

Rezolvati in multimea numerelor reale prin metoda reducerii sistemul de ecuatii :
Va rog , urgent : ([tex] \left \{ {{x-y=-5} \atop -x+3y=19}} \right.
\left \{ {{3x+2y=19} \atop {x+5y=15}} \right. [/tex]

Answer 1

[tex]\it \begin{cases}\it\ \ \ x-y= -5\\ \it-x+3y=19\end{cases}\\ --------- \\ .\ \ \ \ \ \ \ \ \ 2y = 14 \Longrightarrow \ y = 7\ \ \ \ (*)[/tex]

[tex]\it -x+3y=19 \stackrel{(*)}{\Longrightarrow} -x + 3\cdot7=19 \Rightarrow -x = 19-21 \Rightarrow \\\;\\ \Rightarrow -x = -2|_{\cdot(-1)} \Rightarrow x = 2 \\\;\\ S= \{(2,\ \ 7)\}. [/tex]