Question

Stiind ca
a+b=10 şi b+c=12,calculeaza 3·a+7·b+4·c

Answer 1

a+b=10 / ·3
3a+3b=30
b+c=12 /·4
4b+4c=48

3a+3b+4b+4c=30+48
3a+7b+4c=78

Answer 2

a+b=10   si b+c=12  calculeaza 3·a+7·b+4·c

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 ( a+b=10 )×3 ⇒3a+3b=30  (1)

( b+c=12 ) ×4 ⇒4b+4c=48   (2)

Adunam relatiile (1) si (2) si ⇒

3a+3b+4b+4c=30+48⇒ 3a+7b+4c=78