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Daca a+2b+c=16 si 2a+b-3c= -1.Aratati ca :
a) 4a+5b-c=31
b)5a++7b=47

Răspuns :

Morwanneg
La b)

a+2b+c=16 (multiplicam ecuatia cu3)
2a+b-3c= -1

3a+6b+3c=48
2a+b-3c=-1, ecuatiile adunate ajungem la 5a+7b=47 . q.e.d.

La a) a+2b+c= 16 (multiplicam cu 2)
2a+b-3c=-1
2a+4b+2c=32
2a+b=3c= -1
Adunam ecuatiile ajungand la 4a+5b-c= 31, q.e.d.

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