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daca 2a+b+2c=25 si a+b+c=18, atunci (a+c)(3a+2b+3c)=?


Răspuns :

2a+b+2c=25
a+b+c=18- INMULTESTI CU -1=>-a-b-c=-18;scazi cele doua ecuatii si obtii
a+c=7
inlocuiesti in a+b+c=25=>b=11
3a+2b+3c=2b+3(a+c)=3x11+3x7=54
a+c=7
rezultat final:7x54=378