Răspuns:
2a+b=5=>
[tex]a = \frac{5 - b}{2} [/tex]
2-b+3c=7
-b+3c=5
-b+3c=2a+b=5
3c=2a+2b
c=
[tex] \frac{2a + 2b}{3} [/tex]
[tex] \frac{2 \times \frac{5 - b}{2} + 2b}{3} = 5 \\ \\ 5 - b + 2b = 15 \\ \\ - b + 2b = 10 \\ b = 10 \\ [/tex]
inlocuim in a doua
[tex] - b + 3c = 5 \\ - 10 + 3c = 5 \\ 3c = 5 + 10 \\ 3c = 15 = > c = 5 [/tex]
si apoi il aflam si pe a
[tex]a = \frac{5 - b}{2} = > a = \frac{5 - 10}{2} = \frac{ - 5}{2} [/tex]
4a+8b+9c=?
[tex]4 \times \frac{ - 5}{2} + 8 \times 10 + 9 \times 5 = \\ = 2 \times ( - 5) + 80 + 40 \\ = - 10 + 80 + 40 \\ = 70 + 40 = 110[/tex]
