# If f(x) = 2x - 10 ; g (x) = 4x + 20 what is the value of (f + g) (3) ?

Oct 29, 2015

$\left(f + g\right) \left(3\right) = 28$

#### Explanation:

First method:

Add $f \left(x\right) + g \left(x\right)$

$\left(2 x - 10\right) + \left(4 x + 20\right)$

Combine like terms.

$= 6 x + 10$

Then substitute $3$ for $x$.

$= 6 \left(3\right) + 10$
$= 18 + 10$
$= 28$

Second method:

Substitute $3$ into both functions individually.

$f \left(3\right) = 2 \left(3\right) - 10$
$= 6 - 10$
$= - 4$

$g \left(3\right) = 4 \left(3\right) + 20$
$= 12 + 20$
$= 32$

$= - 4 + 32$
$= 28$