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Inverse functions

by Ry122
Tags: functions, inverse
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Ry122
#1
Apr2-07, 01:31 AM
P: 520
how do i find
f(x)^-1 of y=4x+9/2x-3
the answer in the back of the text book is

f(x)^-1=3x+9/2x-4
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christianjb
#2
Apr2-07, 01:39 AM
P: 529
Show your attempt at a solution, or pay me 1 dollar for doing your homework for you (your choice).
Ry122
#3
Apr2-07, 01:48 AM
P: 520
2x=4x+9/y + 3y/y
2x=4x+9+3y/y
How do i move 4x to the other side?

christianjb
#4
Apr2-07, 02:07 AM
P: 529
Inverse functions

is 9/2x in your original post 9/(2x)? Just want to check.
Ry122
#5
Apr2-07, 02:14 AM
P: 520
Heres the full working out:
y(2x-3)=4x+9
2x-3=4x+9/y
2x=4x+9/y + 3
2x=4x+9/y + 3y/y
christianjb
#6
Apr2-07, 02:50 AM
P: 529
You gotta learn to put brackets in your eqns. There's no way anyone could have understood your original problem without the brackets.

y(2x-3)=4x+9
x(2y-4)-3y=9
x=(9+3y)/(2y-4)
Ry122
#7
Apr2-07, 03:17 AM
P: 520
Sorry to bother u again but how
do u get from
y(2x-3)=4x+9 to
x(2y-4)-3y=9
christianjb
#8
Apr2-07, 03:22 AM
P: 529
expand and collect terms in x

y(2x-3)=4x+9
->
y2x-3y=4x+9
->
x(2y)-3y=x(4)+9
->
x(2y-4)-3y=9


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