Tutor.com Linear Equations Session

Sep. 8, 2012

Session Transcript - Math - Algebra, 6/8/2012 12:52PM - Tutor.comSession Date: 6/8/2012 12:52PM
Length: 24.8 minute(s)
Subject: Math - Algebra

System Message
[00:00:00] *** Please note: All sessions are recorded for quality control. ***

rachel (Customer)
[00:00:00] how to solve this problem

Joanetta L (Tutor)

rachel (Customer)
[00:00:54] hello

Joanetta L (Tutor)
[00:01:23] do u want to put your problem on the whiteboard??

rachel (Customer)
[00:01:43] yes I'm writing it out

Joanetta L (Tutor)
[00:01:54] k

rachel (Customer)
[00:03:47] i have it

Joanetta L (Tutor)
[00:04:26] so this is a system of equations.....

rachel (Customer)
[00:04:31] yes

Joanetta L (Tutor)
[00:04:43] what method do you like to use to solve these??

rachel (Customer)
[00:05:47] Im not sure I have no clue what methods there are for this

Joanetta L (Tutor)
[00:06:25] we can use elimination where we get rid of one of the variables.....

rachel (Customer)
[00:06:30] oh

Joanetta L (Tutor)
[00:06:37] and then solve for the one that is left....
[00:06:45] does that sound familiar??

rachel (Customer)
[00:06:40] ok
[00:06:52] yes

Joanetta L (Tutor)
[00:07:03] good...
[00:07:18] so we need to rewrite the bottom equation...
[00:07:28] so it is in standard form.....

rachel (Customer)
[00:07:24] ok

Joanetta L (Tutor)
[00:07:36] just like the top one...
[00:08:14] ok??

rachel (Customer)
[00:08:24] oh yes i remember you match up the variables

Joanetta L (Tutor)
[00:08:38] right...
[00:08:52] do u know what comes next??

rachel (Customer)
[00:09:03] do you subtract?

Joanetta L (Tutor)
[00:09:48] first we need to get one of the variables with opposite signs and same coefficients....
[00:10:02] does that make sense??

rachel (Customer)
[00:10:08] kind of ?

Joanetta L (Tutor)
[00:10:30] so let's look at the top equation....

rachel (Customer)
[00:10:30] ok

Joanetta L (Tutor)
[00:10:57] which variable would u like to get rid of by adding it to the bottom....
[00:11:08] after multiplying by some number......

rachel (Customer)
[00:11:17] y

Joanetta L (Tutor)
[00:11:29] ok...
[00:11:53] so what do we need to do to 5y so that we can cancel out the 10y??

rachel (Customer)
[00:12:45] do you turn 5y into -5y-10y?

Joanetta L (Tutor)
[00:13:20] we need to multiply 5y by -2 ....
[00:14:09] of course...we have to mult everything in the equation...not just the 5y

rachel (Customer)
[00:14:18] oh

Joanetta L (Tutor)
[00:14:34] now what should we do...

rachel (Customer)
[00:15:14] im not sure..

Joanetta L (Tutor)
[00:15:40] let's add the 2 equations together so the y's cancel out.....
[00:15:45] but wait....
[00:15:54] everything in this one cancels....
[00:15:57] right??

rachel (Customer)
[00:16:08] yes

Joanetta L (Tutor)
[00:16:31] so when we get an answer like this...

rachel (Customer)
[00:16:27] so theres no solution or 1 solution?

Joanetta L (Tutor)
[00:16:52] no.....there are MANY solutions......

rachel (Customer)
[00:17:20] oh yeah i always got confused with that

Joanetta L (Tutor)
[00:17:44] let me show u a trick....to remember....
[00:18:23] so pretend we don't know the answer....

rachel (Customer)
[00:18:24] ok

Joanetta L (Tutor)
[00:18:42] what do u notice about all the numbers in this system.....?

rachel (Customer)
[00:19:05] they can be divided evenly

Joanetta L (Tutor)
[00:19:37] so I could divide the second eq by 2 and what happens....

rachel (Customer)
[00:21:39] you get 2
[00:22:22] ok

Joanetta L (Tutor)
[00:22:46] now we see that this is actually 2 ways to write the same equation.....

rachel (Customer)
[00:22:39] i get it now thank you

Joanetta L (Tutor)
[00:22:52] np
[00:22:59] so when this happens....
[00:23:12] u know that if you graphed the '2' lines......
[00:23:22] it would actually only be one line
[00:23:38] and there are many solutions to the equation...

rachel (Customer)
[00:23:43] oh ok thanks that really helped

Joanetta L (Tutor)
[00:23:56] awesome!!!
[00:24:07] Thanks for using tutor.com today....

rachel (Customer)
[00:24:12] welcome

Joanetta L (Tutor)