Given $f (n) = n - 4$ $f(n)=n-4$ and $g (n) = 2 n$ $g(n)=2n$ , how do you find $3 f (n) + 5 g (n)$ $3f(n)+5g(n)$ ?

Question

4579 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-10-26T11:31:36

$3 f (n) + 5 g (n) = 13 n - 12$ $3f(n)+5g(n)=13n-12$

$f(n)=n-4.............(i)$
$g(n)=2n..................(ii)$

To find out: $3f(n)+5g(n)$

Multiply $(i)$ by $3$ .
$3f(n)=3(n-4)$
$implies 3f(n)=3n-12...................(iii)$

Multiply $(ii)$ by $5$ .
$5g(n)=5(2n)$
$implies 5g(n)=10n......................(iv)$

Now, Add $(iii)$ and $(iv)$

$implies 3f(n)+5g(n)=3n-12+10n$
$implies 3f(n)+5g(n)=13n-12$

Given f(n)=n-4f(n)=n−4f(n)=n-4 and g(n)=2ng(n)=2ng(n)=2n, how do you find 3f(n)+5g(n)3f(n)+5g(n)3f(n)+5g(n)?