Question

daca a+b=1,2 si b+c=2,3 atunci suma 3a+7b+4c este egala cu

Answer 1

3a+7b+4c=3a+3b+4c+4c=3(a+b)+4(b+c)=3*1,2+4*2,3=3,6+9,2=12,8.

Answer 2

a+b=1,2
b+c=2,3
a+2b+c=3,5
a=1,2-b
c=2,3-b
1,2-b+2b+2,3-b=3,5
2b=0=>b=0
a=1,2
c=2,3
3a+7b+4c=
3*1,2+7*0+4*2,3=
3,6+0+9,2=
12,8