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sistem de ecuație prin metode substituției
2(x+y-1)+3(x-y+2)=15
5(x-y-1)+2(x-y+4)=-4
urgeeent


Răspuns :

[tex]\left\{\begin{matrix}
2(x + y - 1) + 3(x - y + 2) = 15\\

5(x - y - 1) + 2(x - y + 4) = - 4\end{matrix}\right.[/tex]

[tex]\left\{\begin{matrix}
2x + 2y - 2 + 3x + 3y + 6 = 15\\

5x - 5y - 5 + 2x - 2y + 8 = - 4\end{matrix}\right.[/tex]

[tex]\left\{\begin{matrix}
5x + 5y + 4 = 15\\

8x - 7y + 3 = - 4\end{matrix}\right.[/tex]

[tex]\left\{\begin{matrix}
5x + 5y = 15 - 4\\

8x - 7y = - 4 - 3\end{matrix}\right.[/tex]

[tex]\left\{\begin{matrix}
5x + 5y = 11\\

8x - 7y = - 7\end{matrix}\right.[/tex]

[tex]x = \frac{11 - 5y}{5} [/tex]

[tex]8x - 7y = - 7[/tex]

[tex]8 \times \frac{11 - 5y}{5} - 7y = - 7[/tex]

[tex] \frac{88 - 40y}{5} - 7y = - 7 \: | \times 5[/tex]

[tex]88 - 40y - 35y= - 35[/tex]

[tex] - 40y - 35y = - 35 - 88[/tex]

[tex] - 75y = - 123 \: | \times ( - 1)[/tex]

[tex]75y = 123[/tex]

[tex]y = \frac{123}{75} [/tex]

[tex]y = 1.64[/tex]

[tex]5x + 5y = 11[/tex]

[tex]5x + 5 \times 1.64 = 11[/tex]

[tex]5x + 8.2 = 11[/tex]

[tex]5x = 11 - 8.2[/tex]

[tex]5x = 2.8[/tex]

[tex]x = \frac{2.8}{5} [/tex]

[tex]x = 0.56[/tex]