Question

Daca a+b=15 si2b+3c=24 calculati
a) a+3b+3c;
b). 2a+8b+9c

Answer 1

a) facem inlocuiri:
din primul calcul:
a=15-b
3b lasam intact
din al doilea calcul:
3c=24-2b    =>
15-b+3b+24-2b=15+24=39
b)aceleasi inlocuiri:
daca a=15-b | *2
atunci 2a=30-2b
8b ramane intact:
3c=24-2b    |*3
9c=72-6b
facem inlocuiri:
30-2b+8b+72-6b=30+72=102

Answer 2

A + B = 15
2B + 3C = 24
a) a + 3b + 3c = (a + b) + (2b + 3c) = 15 + 24 = 39
b) 2a + 8b + 9c = 2(a + b) + 3(2b + 3c) = 2 * 15 + 3 * 24 = 30 + 72 = 102