1. ## Simultaneous Equations

Through using substitution how can I solve

3p-3 = q
and
7p=1+4q

so that p=-1 and q=-2

I am really interested in the working out, the how and the why. If that makes sense.

2. ## Re: Simultaneous Equations

Substitute the first equation (q=...) in the second equation therefore you get a first degree equation in p.

3. ## Re: Simultaneous Equations

Thats the problem I have rewritten the first equation so that p = 3q+3/3 and tried to substitute it into 7p = 1 + 4q but I am getting nowhere.
Any hints would be appreciated

4. ## Re: Simultaneous Equations

Yes, but you see the first equation is q=..., so you can directly substitute $q=3p-3$ in the second one therefore you get:
$7p=1+4(3p-3)$
Solve this equation for $p$, afterwards you can find $q$

5. ## Re: Simultaneous Equations

Originally Posted by planetdomi
Through using substitution how can I solve

3p-3 = q
and
7p=1+4q

so that p=-1 and q=-2

I am really interested in the working out, the how and the why. If that makes sense.

So sorry I go the equations wrong

3p-3 = 3q

and

7p = 1 + 4q

6. ## Re: Simultaneous Equations

No problem, it's just the same way. If you divide in the first equation every side by 3 then you get $p-1=q$, now substitute this in the second equation therefore the equation becomes:
$7p=1+4(p-1)$

What do you get for $p$? And $q$?

7. ## Re: Simultaneous Equations

Feel like a fool for not getting it
Makes perfect sense now

thanks

8. ## Re: Simultaneous Equations

Originally Posted by planetdomi
Feel like a fool for not getting it
Makes perfect sense now

thanks
You're welcome! You don't have to feel like a fool, everyone has to learn, but it's important to exercice a lot.