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X+y=10 si y+2×z=12 afla 3x+8y+10z

Răspuns :

X+Y=10
Y+2Z=12
X=2
2+Y=10
Y=8
8+2Z=12
Z=2
6+64+20=90

[tex]\it x+y=10|_{\cdot3} \Longrightarrow 3x+3y=30 \ \ \ (1) \\\;\\ y+2z=12 |_{\cdot5}\Longrightarrow 5y+10z = 60 \ \ \ (2) \\\;\\ (1), (2) \Longrightarrow 3x+8y+10z = 90 [/tex]