Solve the following equations algebraically

2x + y = 0

−2x −3y = 8 im stuck i can do the easy ones when in the format y=mx+c

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- Sep 11th 2009, 09:42 PMrealisticsim equations
Solve the following equations algebraically

2x + y = 0

−2x −3y = 8 im stuck i can do the easy ones when in the format y=mx+c - Sep 11th 2009, 09:47 PMVonNemo19
- Sep 11th 2009, 09:49 PMrealistic
- Sep 11th 2009, 09:57 PMVonNemo19
It's called the substitution method.

EG

We have the sim equations

and

Then we solve for a variable in one of the equations and substitute for the variable in the other

Now we sub for y in the other

solve for x and we can determine the solution

Now we put back in the original for x.

Do you see? - Sep 11th 2009, 10:00 PMrealistic
- Sep 11th 2009, 10:06 PMVonNemo19
- Sep 11th 2009, 10:13 PMrealistic
- Sep 11th 2009, 10:24 PMVonNemo19
Think of it like a game, with the object being to line thx's and y's up underneath of each other and then add or subtract them to get rid of one of them.

You can see here that the x's and y's are not right underneath of each other, but wait...

Now the x's and y's are lined up. But remember that the object is to add (or subtract) so that I eliminate one of the variables. To do this I have to do a little trick with multiplication...

Now look! The x's and y's are still lined up, but now if I subtract the two equations, the x's will dissapear and I can solve for y!

Do you see? - Sep 11th 2009, 10:29 PMrealistic
- Sep 11th 2009, 10:31 PMVonNemo19
- Sep 12th 2009, 12:28 AMrealistic
been doing alot of them and just got stuck at this one

3y +2x +10 = 0

2y = x −2

=

3y +2x +10 = 0

2y - x +2 = 0

x by 2? then add both? i tried but got wrong answer (Headbang) - Sep 12th 2009, 06:27 AMVonNemo19
- Sep 12th 2009, 06:56 AMrealistic
- Sep 12th 2009, 07:00 AMMatt Westwood
Add them, don't subtract them.

- Sep 12th 2009, 07:02 AMrealistic