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Daca 3a+2b+4c=494 si b+2c=157, calculati ab+2ac

Răspuns :

3a+2b+4c=494
3a+2 (b+2c)=494
3a+2*157=494
3a=494-314=> 3a=180=>a=60
ab+2ac=a(b+2c)=60*157=9420