If f(x)=4[x-1] and g(x)=x+1, how do you find f(g(-1))?

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If f(x)=4[x-1] and g(x)=x+1, how do you find f(g(-1))?

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Answer 1 · 2015-09-11T12:43:23

$f(g(-1)) = -4$

Explanation:

When you have an expression:
$f(y)$ ,
this means that you should plug in whatever $y$ is into $x$ in the function $f(x)$ . That is, replace every instance of $x$ with $y$ .

There are two ways to find $f(g(-1))$
The first is to solve from the inside out.

Plug in $-1$ into $g(x)$ to get $g(-1)$ :
$g(x) = x+1$
$g(-1) = -1 +1$
$color(blue)(g(-1) = 0)$

Then, plug in $g(-1)$ into $f(x)$ :
$f(x) = 4[x-1]$
$f(g(-1)) = 4[0-1]$
$color(blue)(f(g(-1)) = -4)$

The second way is to get $f(g(x))$ first, then plug in $-1$ :

$color(red)(f(x) = 4[x-1])$
$color(blue)(g(x) = x+1)$

$color(red)(f(color(blue)(g(x)))) = color(red)(4[color(blue)(x+1)-1])$

Then, you can plug in $-1$

$f(g(-1)) = 4[-1 +1 -1]$
$color(blue)(f(g(-1)) = -4)$

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If f(x)=4[x-1] and g(x)=x+1, how do you find f(g(-1))?

1 Answer

Explanation:

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