Question

Va rog mult sa ma ajutati!!! E URGENT!!!
1. Daca a+b=8 si b+c=12 sa se calculeze 2a+5b+3c
2. Daca a+2b=5 si b+3c=4 sa se calculeze 3a+10b+12c
E URGENT!!!

Answer 1

3a+3b+2b+2c=3(a+b)+2(b+c)=3*8+2*12=24+24=48
3a+6b+4b+12c=3(a+2b)+4(b+3c)=3*5+4*4=15+16=31

Answer 2

a + b = 8 ⇒ a = 8 - b
b + c = 12 ⇒ c = 12 - b
2a + 5b + 3c
inlocuim in a doua expresie
2 ( 8 - b ) + 5 b + 3 ( 12 - b )=
16 - 2b + 5 b + 36 - 3b= 52

2. a + 2b = 5 ⇒a = 5 - 2b
    b + 3c = 4⇒3c =4 - b ⇒c = (4 - b ) : 3
3a + 10 b  + 12 c =
3 ( 5 - 2b ) + 10 b + 12 ( 4 - b ) : 3=
 15 - 6 b + 10 b +( 48 - 12 b) : 3=
15 - 6b + 10 b + 16 - 4b =31