# Similtanious equation help?

1. May 1, 2010

### 3nder

Just doing a bit of math homework and im stuck on 2 questions

the first one is a similtanoius equation and goes like this

y = x - 1
y = x2 -3

ive been trying for about half an hour and all i end up with is

y = (square root of) y - 2

im not sure if it's right, it does not look it.

the 2nd question i dont know the name of and looks like

72x = 49

i dont even know where to begin on that, i just have to factorise it.

2. May 1, 2010

### rock.freak667

Can you write 49 in any way that relates to 7?

3. May 1, 2010

### 3nder

for the 2nd question i know that x = 1 but i dont know how to write the proof, like in another question how would i do

43-x = 8x

1st question solved thankyou rock.freak667

Last edited: May 1, 2010
4. May 1, 2010

### rock.freak667

It all revolves around how you can write the base numbers. If you have am=an then m=n.

So if you have 36=62x, then you can write this as 62=62x which means that 2=2x and hence x=1.

5. May 1, 2010

### xcvxcvvc

Also remember how a power to a power behaves:
$$(a^b)^c = a^{bc}$$

so:
$$(8)^x=(2^3)^x=2^{3x}$$

and

$$(4)^{3-x}=(2^2)^{3-x}=2^{6-2x}$$

edit: I misread and thought you said this problem's solution was x = 1. My bad!

6. May 1, 2010

### rock.freak667

Right so now you have

$$2^{6-2x}=2^{3x}$$

so what is x?