LLD101

EMP · Last edited by EMP on Sun Jan 29, 2006 4:43 pm; edited 1 time in total

how would you take the inverse of
f(x)= 2x^4 - 3x + 5

what is the answer and how did you get it. thanks

EDIT:
what are accumulation functions? (used in calc classes, nothing of that money thing because I tried googling it. )

OSA · Posted: Sat Jan 28, 2006 11:10 pm Post subject:

Isn't the inverse just 1 over all that?

I dunno.

www.math.com

Check there, they might have it.

krajee · Joined: 27 Aug 2004 Posts: 6579 9.68 Silvarrr

lld_master · Joined: 04 Oct 2004 Posts: 412 0.00 Silvarrr

all you have to do is switch the X and the Y and then again make it all equal to Y.

Meaning,

it is:

f(x) = 2x^4 - 3x +5
Y = 2x^4 - 3x +5
X = 2Y^4 - 3Y +5
(X - 5 + 3y) = 2Y^4
(X - 5 + 3y)/2 = Y^4
Y = foruthrootof((X - 5 + 3y)/2)

answer:
y = foruthrootof((X - 5 + 3Y)/2)

EMP · Posted: Sun Jan 29, 2006 4:42 am Post subject:

I can just leave it like that? Don't I have to put all of the 'y's on one side or something? But ((x - 5 + 3y)/2)^(1/4) = y sounds like a plausible answer. The only problem I have with it is that if I were to attempt tio graph it, how would I be able to plug in the y-values if I don't know it?

Thanks

B[x] · Posted: Sun Jan 29, 2006 12:09 pm Post subject:

LLD_Pie · Joined: 22 Jun 2004 Posts: 515 0.00 Silvarrr

to graph it first find its intercepts

so set y to 0 and you get

if y = 0 then x = 5 because 0 / anyting = 0

if y = 1 then

1 = (x-5)/(2-3)
1 = (x-5)/(-1)
-1 = x-5
x = 4

if y = 2 then

2 = (x-5)/(13)
16 = (x-5)
x = 21

if y = -1 then

-1 = (x-5)/(-5)
5 = (x -5)
x = 10

somone check me on this but im pretty sure thats how its done...

B[x] · Posted: Sun Jan 29, 2006 1:02 pm Post subject:

OHHHHHHHHH!! For some reason I thought he wanted it in y= form so that he could plug it into his calculator for an easy quick graph. Oh, okay. Yeah, to graph it by hand (if that's what you want to do), just pick arbitrary y-values and solve for x.

EMP · Posted: Sun Jan 29, 2006 1:33 pm Post subject:

ahh, thanks so much guys.

ATOMICMAN · Posted: Sun Jan 29, 2006 5:11 pm Post subject:

god i hated calc =(

Royale · Posted: Sun Jan 29, 2006 5:31 pm Post subject:

I got kind of dizzy reading this thread.

Visual Tactics · Posted: Sun Jan 29, 2006 5:32 pm Post subject:

Uh oh, i'm taking calc next year... Sad

lld_master · Joined: 04 Oct 2004 Posts: 412 0.00 Silvarrr

to graph this using a calculator would be easy since there is an Inverse function on the TI-83

for example it would be something like this:

y1=Inverse(2x^4 - 3x +5)

done!

krajee · Joined: 27 Aug 2004 Posts: 6579 9.68 Silvarrr

B[x] · Posted: Sun Jan 29, 2006 11:06 pm Post subject: