Question

Considere as funções f(x) = 4x + 5 e g(x) = 2x + 1. O valor de k tal que f(g(k)) = 25

Answer 1

Fx=4x+5
Gx= 2x+1

4.(2(x)+1)+5=25
8(x)+4+5=25
8x=25-5-4
8x=16
x=2

x=2
4.(2(x)+1)+5=25 
4.(2(2)+1)+5=25
4(5)+5=25
25=25

Answer 2

$Ola'~~~~\mathbb{JESSI} \\ \\ Temos: \\ \boxed{f(x)=4x+5} \\ g(x)=2x+1~~--\ \textgreater \ devemos~saber~g(k), ent\~ao~seria: \\ \boxed{g(k)=2k+1} \\ \\ Nos~indica~que: \\ \boxed{f(g(k))=25} \\ \\ Calculemos~''k''~quanto~vale, veja: \\ f(g(k))=4g(x)+5 \\ \underbrace{f(g(k))}_{25}=4(2k+1)+5 \\ 25=4(2k+1)+5 \\ 25=8k+4+5 \\ 25=8k+9 \\ 25-9=8k \\ 16=8k \\ k= \frac{16}{8} \\ \boxed{\boxed{k=2}} \\ \\ \\\mathbb{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} \\ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Espero~ter~ajudado!!$