# Inverse func.

1. Aug 1, 2011

### Nelo

1. The problem statement, all variables and given/known data

y = 3
___
2(x-3)

2. Relevant equations

3. The attempt at a solution

Ive tried several times, I cant get the steps down. They say use reverse bedmass, and I dont understand.

Here's what i did.

y= 3/2(x-3)

x= 3/2(y-3)

x= 3/2y-6
x+6=3/2y

x+6
___ = 3
2

Which is already wrong, as you can see. Can someone please tell me the step so i can stop being stuck on this for 2 hours? =)

2. Aug 1, 2011

### Ivan92

"x= 3/2y-6"

You were correct up to here. If it helps, write parenthesis in the denominator.

x=$\frac{3}{(2y-6)}$

What you did was just cancelled out the 6 in the denominator which you cannot do. Our objective is to get y by itself. Do that by multiplying 2y-6 to both sides. That should get rid of the fraction and leave you with.

x(2y-6)=3

Try getting y by itself from here.

3. Aug 1, 2011

### Nelo

Ok...

x = 3 / (2y-6)

x(2y-6) 3
_______ = _____
(2y-6) (2y-6)

2xy-6x 3
______=_____
2y-6 2y-6

Pretty sure im already wrong. .. .

4. Aug 1, 2011

### Ivan92

When I mean multiply both sides you don't do it like this:

$\frac{2y-6}{2y-6}$ x=$\frac{3}{2y-6}$$\frac{2y-6}{2y-6}$

$\uparrow\uparrow\uparrow\uparrow$ That is a no no.

You do it like this:

x($\frac{2y-6}{1}$)=$\frac{3}{2y-6}$($\frac{2y-6}{1}$)

Notice how the (2y-6) in the right side would cancel out. That would leave us with this.

x(2y-6)=3

Remember this: If you do anything to one side, you MUST do it to the other side of the equation.

5. Aug 1, 2011

### Nelo

So... the x still factors into 2y-6 on both sides..? your eq would give 2xy-6x/x on the left side..

6. Aug 1, 2011

### Ivan92

What do you mean "factors on both sides)? My equation would not leave you with a fraction (though the answer would be a fraction). Try distributing the x term to (2y-6). Then just solve for y.

*Update: I see what you did. No that is wrong. Remember your algebraic properties:

a*$\frac{b}{c}$=$\frac{ab}{c}$

7. Aug 1, 2011

### Nelo

So, i did it like this..

2x(y-3) = 3

2x*y -6x =3

2x*y = 6x+3

y= 6x+3 /2x

y= 3x +3/2x

The answer is 2/3x +3 , however. Why is the x on the bottom?

8. Aug 1, 2011

### Ivan92

Starting from here:
"2xy = 6x+3"

We would divide 2x to get y by itself.

$\frac{2xy}{2x}$=$\frac{6x+3}{2x}$

I see you split the fraction on the right side to divide 6x/2x, however you forgot to cancel out the x. However you cannot divide 3/(2x), so that is why 2x is in the denominator. The answer would look like this.

y=$\frac{3}{2x}$+3

I do not see how the right answer is: "2/3x +3" (assuming this is (2/(3x))+3) the 3 is supposed to be in the numerator and 2x is supposed to be in the denominator.