Let f(x) = x2 - 16. Find f-1(x).

(x2 means x to the 2 )

Question

Let f(x) = x2 - 16. Find f-1(x).

(x2 means x to the 2 )

yumeybitaa · Answer

(f-1--> means f to the -1 )

anonymous · Answer

$$f(x)=x^2-16$$ and you want 
$$f^{-1}(x)$$ right?

yumeybitaa · Answer

esactly

anonymous · Answer

ok good
tell the idiot who wrote this question that since 
$$y=x^2-16$$ is a parabola, it is evidently not a one to one function 
so for example 
$$f(5)=f(-5)=9$$ that there is no function 
$$f^{-1}(x)$$

anonymous · Answer

on the other hand, we can still solve 
$$x=y^2-16$$ for $y$
we get 
$$x+16=y^2\
\pm\sqrt{x+16}=y$$

anonymous · Answer

Are you given a domain and range?

anonymous · Answer

so i have no idea what you are supposed to put
perhaps 
$$f^{-1}(x)=\pm\sqrt{x+16}$$

anonymous · Answer

the $\pm$ part tells you it is not a function

yumeybitaa · Answer

yea i think that's the answer

anonymous · Answer

ask whoever wrote this question if they know what a function is, and if so, how you can have a function that is either plus or minus depending on your mood
the answer is you cannot

yumeybitaa · Answer

well this question is from my exam of flvs

anonymous · Answer

let me make a guess
FLVS??

anonymous · Answer

how did i know?

anonymous · Answer

i keep asking for question id numbers from people who ask these questions'
but no one ever wants to tell me

anonymous · Answer

there questions are the most poorly written i have ever seen
written by people who have no idea about math
it is a sin
you should insist on going to a real school, unless of course the schools in florida are actually even worse

anonymous · Answer

*their

yumeybitaa · Answer

i left school because of bullying .....but hey can you help me with another one ?

anonymous · Answer

sure

yumeybitaa · Answer

Let f(x) = -4x + 7 and g(x) = 10x - 6. Find f(g(x)).

-40x+24
-40x + 31
-40x+64
-40x+70

anonymous · Answer

ok we work from the inside out 
$$f(g(x))=f(10x-6)$$ 
since 
$$\large f(\heartsuit)=-4\heartsuit+7$$ you get $$f(10x-6)=-4(10x+6)-7$$ now some algebra

anonymous · Answer

ok i messed that up hold on

yumeybitaa · Answer

okay :)

anonymous · Answer

$$f(10x-6)=-4(10x-6)+7$$thats better

anonymous · Answer

now algebra 
$$-40x+24+7\
-40x+31$$

anonymous · Answer

go with B

anonymous · Answer

got more or is that it?

yumeybitaa · Answer

if you wanna keep helping me i have 2 more

anonymous · Answer

sure no problem

yumeybitaa · Answer

Let f(x) =  12 over the quantity of 4 x + 2. Find f(-1).|dw:1417017843604:dw|

anonymous · Answer

$$y=\frac{12}{4x+2}$$

anonymous · Answer

switch x and y 
$$x=\frac{12}{4y+2}$$ and solve for $y$

anonymous · Answer

$$x=\frac{12}{4y+2}\
x(4y+2)=12$$
$$4xy+2x=12\
4xy=12-2x\
y=\frac{12-2x}{4x}$$

anonymous · Answer

other in answers include 
$$f^{-1}(x)=\frac{6-x}{2x}$$

yumeybitaa · Answer

this is a little bit complicated

anonymous · Answer

did you see an answer that looked like 
$$f^{-1}(x)=\frac{6-x}{2x}$$

yumeybitaa · Answer

yes

yumeybitaa · Answer

-6
-2
2
6

I'm guessing is 6

anonymous · Answer

oh wait, all you need is $f(-1)$?

anonymous · Answer

$$f(-1)=\frac{12}{4\times (-1)+2}=\frac{12}{-2}=-6$$

anonymous · Answer

go with $-6$

yumeybitaa · Answer

phh okay thank you

anonymous · Answer

next?

yumeybitaa · Answer

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

anonymous · Answer

this one is quick
solve 
$$2x+2=4$$ for $x$ in two steps

anonymous · Answer

$$2x+2=4\
2x=2\
x=1$$

yumeybitaa · Answer

i got that one right , i did it on my own but i wanted to see if i was right thank you

anonymous · Answer

yw

yumeybitaa · Answer

that's all thank you for your help