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Edyadrian21
a fost răspuns

2a+b-3c=15
a-4b+8c=25
Calculati 5a-11b+21c.

Răspuns :

Mihaela0205
2a+b-3c=15
a-4b+8c=25
Daca vei inmulti fiecare termen al ecuatiei a 2-a, vei obtine:
a-4b+8c=25 / *3
3a - 12b + 24c = 75
Apoi aduni cele 2 ecuatii, astfel:
2a+b-3c + 3a-12b+24c= 15 + 75
2a+3a=5a
b-12b=-11b
-3c+24c=21c
=> 5a-11b+21c = 90 :)