# How do you do system of equations?

• Mar 9th 2008, 08:34 PM
topaz192
How do you do system of equations?
Ok, i was just on a site for tutoring but it isn't making much sense to me!
What steps do i follow through when doing this?

y=3x+7
y=x-9
• Mar 9th 2008, 08:38 PM
topher0805
To solve it, set the two expressions equal to each other.

\$\displaystyle 3x+7 = x-9\$

Then solve for x, to get:

\$\displaystyle x=-8\$
• Mar 9th 2008, 08:45 PM
topaz192
ok, so on one like

y=2x+3
y=3x+1

itll be 2x + 3=3x+1?

and solve from there? aren't you suppose to change signs when bringing it over?
• Mar 9th 2008, 08:53 PM
topher0805
Switch signs? Sort of, let me give you a step by step version of this:

\$\displaystyle 2x+3=3x+1\$

Subtract 1 from both sides:

\$\displaystyle 2x+2=3x\$

Subtract 2x from both sides:

\$\displaystyle
2=1x\$

So:

\$\displaystyle x=2\$

Do you see?
• Mar 9th 2008, 09:02 PM
topaz192
I think so.

So on one like

y=2x-10
y=4x-8

itll be 2x-10 = 4x-8

2x=-2

x=-1?

ha i suck at combining like terms and what not lol.
• Mar 9th 2008, 09:14 PM
topher0805
Yeah, it looks like you've got it now.
• Mar 9th 2008, 09:17 PM
topaz192
Yay! Thanks for your time! = ]
• Mar 10th 2008, 04:55 AM
topsquark
Quote:

Originally Posted by topaz192
Ok, i was just on a site for tutoring but it isn't making much sense to me!
What steps do i follow through when doing this?

y=3x+7
y=x-9