# Thread: algebra

1. ## algebra

To sove a economic question i need to use algebra first.

P= - 1/4Qd+6.75

P = 1/2Qs + 2

So i got for the first step:

1/4 Qd = - p + 48

1/2 Qs = p - 2

but i need to get the 1/4 and 1/2 on the right side which i don't know how.

I would reall appreciate your help.

2. Originally Posted by abc
To sove a economic question i need to use algebra first.

P= - 1/4Qd+6.75

P = 1/2Qs + 2

So i got for the first step:

1/4 Qd = - p + 48

1/2 Qs = p - 2

but i need to get the 1/4 and 1/2 on the right side which i don't know how.

I would reall appreciate your help.
$\displaystyle - \frac{1}{4} Qd + 6,75 = \frac{1}{2} Qs + 2$

(Multiply by 4 straight through)

$\displaystyle -Qd + 27 = 2Qs + 8$

$\displaystyle 2Qs + Qd = 21$

Can you take over from here?

EDIT: Hint: Isolate Qd and set it back into the first equation

3. Originally Posted by janvdl
$\displaystyle - \frac{1}{4} Qd + 6,75 = \frac{1}{2} Qs + 2$

(Multiply by 4 straight through)

$\displaystyle -Qd + 27 = 2Qs + 8$

$\displaystyle 2Qs + Qd = 21$

Can you take over from here?

EDIT: Hint: Isolate Qd and set it back into the first equation
It think you have used it as one formula but they are seperate so i need to get 1/4 in the first formula to the right side so it is in the format of Qd=.... the same applies to the 1/2Qs one. So in the end i will have two answers. One being Qd equals and one Qs equals.

4. 1/2 Qs = p - 2
Good so far. Now divide both sides of the equals sign by 1/2.

$\displaystyle \frac {1/2 Qs}{1/2} = \frac {p-2}{1/2}$
Qs = 2(p-2)
Qs = 2p-4

P= - 1/4Qd+6.75
Add 1/4Qd to both sides:
P+1/4Qd = -1/4Qd+6.75+1/4Qd
P+1/4Qd = 6.75

Now subtract P from both sides
P+1/4Qd-P = 6.75-P
1/4Qd = 6.75 -P

Then divide both sides by 1/4
$\displaystyle \frac {1/4Qd}{1/4} = \frac {6.75-p}{1/4}$
Qd = 4(6.75 - p)
Qd = 27-4p