Another functions questions?

Question

anonymous · Answer

Let f(x) = 2x + 2. Solve f-1(x) when x = 4.

 1

 3

 4

 10

anonymous · Answer

2x + 2
2 (4) + 2
8 + 2
10

But I don't get what the f-1(x) is so I don't know if im right or not?

anonymous · Answer

@Mokeira

mokeira · Answer

it simply means inverse

anonymous · Answer

so I'm right? inverse = opposite doesn't it?

anonymous · Answer

or its 1 actually?

mokeira · Answer

This is how you do it
$$2x+2=\frac{ 1 }{ 2 }x+2$$
you inverse the 2 that has x

mokeira · Answer

then substitute

mokeira · Answer

hope you get what I am trying to say

mokeira · Answer

@CrazyTurtle483

anonymous · Answer

sorry i had to go get dogs in

anonymous · Answer

yea i kinda do it's kind of confusing

anonymous · Answer

when i do it on paper i get 1

mokeira · Answer

basically it means inverse the value that has x...in this case, 2x, we inverse 2

mokeira · Answer

you should get 4

mokeira · Answer

$$\frac{ 1 }{ 2 }x+2=(\frac{ 1 }{ 2 }\times 4)+2$$
$$=2+2$$
=4

phi · Answer

Let f(x) = 2x + 2. Solve f-1(x) when x = 4.

f(x) returns a number.  call it y.
$f^{-1}(y)$  takes the out of f(x), and returns the x

phi · Answer

in other words
$$ f^{-1}(4) $$ means the output of f(x) = 4
and we want to find x.
 f(x) = 2x + 2
4 = 2x+2
solve for x

add -2 to both sides: 4-2 = 2x +2-2
2= 2x
divide both sides by 2
1= x
1 is the answer