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3a+2b+2c=45. ,a+2b+2c=99 .a+b+c=?

Răspuns :

3a+2b+2c=45 => 3a +2(b+c)=45
a+2b+2c=99=> a+2(b+c)=99=>2(b+c) =99-a
3a+99-a=45
2a=-54
a=-27
3*(-27)+2(b+c)=45
-81 +2(b+c)=45
2(b+c)=126
b+c=63
=>a+b+c=63+(-27) =36

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