Question

Se stie ca:2×a+2×b+2×c=168,c-b=11 si a+b=45.Care este a?

Answer 1

2×a+2×b+2×c=168
c-b=11
a+b=45
dam factor comun si inlocuim
2(a+b)+2c=168
2×45+2c=168
90+2c=168
2c=168-90
2c=78
c=78:2=39
c-b=11
39-b=11
b=39-11=28
a+b=45
a+28=45
a=45-28
a=17
si inlocuim ce am aflat
2×17+2×28+2×39=
34+56+78=168

Answer 2

2×a+2×b+2×c=168
Il dam factor comun pe 2.
2×(a+b+c)=168

c-b=11....c=11+b

a+b=45

Inlocuim....

2×(45+11+b)=168
56+b=168:2
56+b=84
b=84-56
b=28

a+b=45
b=28
inlocuim....
a+28=45
a=45-28
a=17

c-b=11
c-28=11
c=11+28
c=39

verificare:
2×a+2×b+2×c=168
2×17+2×28+2×39=34+56+78=168