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A+b=14
b+c=9
calculati: 2xa+5xb+3xc=?


Răspuns :

a+b=14(inmultim cu2)
2a+2b=28
b+c=9(inmultim cu 3)
3b+3c=27
2a+5b+3c=55
[tex]a+b=14\ |\cdot2\longrightarrow 2a+2b=28\\b+c=9\ |\cdot3\longrightarrow 3b+3c=27\ |(Adunam\ cele\ doua\ relatii)\\\\2a+2b+3b+3c=27+28\\\\\boxed{2a+5b+3c=55}[/tex]