January 19, 2011

Systems of Linear Equations: Elimination Method (CA SS: 9.0)

p.371 (1-19:odd, 31, 33)

26 comments:

jose c per3 said...

how do u get the y axis for the first problem

MarcusB. per.6 said...

Journal Entry:
Today in math class, we collected the homework, after going over some questions. We did notes on the elimination method.
Example...
5x+3y=17
5x-2y=-3

5x+3y=17 5x-2y=-3
5x-2y=-3 5x-2(4)=-3
5x-8=-3
5y 20 +8 +8
____ =_____

5 5 5x 5
___ = ___
y=4 5 5

x=1

Answer is (1,4)

MarcusB. per.6 said...

aw man... it messed it up

MarcusB. per.6 said...

What happens if you don't do the journal entry on the day you are supposed to do it?

MLYHOOPS said...

u get no credit marcus.... if u dont do it that day ur supposed to.

Natasha L Per.4 TA said...

~Journal Entries~

Period 2:
Period 3:
Period 4:
Period 5:
Period 6: Marcus B.

@Jose, I have no clue what you are talking about.

@ Marcus, Yeah what Matt said.... :3

MLYHOOPS said...

hey natasha. how do u do # 3? i failed i got 9,8 but i look at the back and it says 3,5 so i need help

MLYHOOPS said...

oh never mind. it says use the addition method..... i used the wrong method.... haha i failed

Natasha L Per.4 TA said...

@Matt, good job you solved the problem by yourself.

I'm sure Sean mentioned this before but I just want to emphasize the fact that, we as the TA's, we don't have a copy of the math-book. Telling us simply "I need help with number _ " will not help you in any way.

I also want to state that OTHER students should be helping others. We, as the TA, will help you but make notice that other students should be helping....

Sorry about my rant, I guess I am in a bad mood.....

MLYHOOPS said...

ok natasha

MarcusB. per.6 said...

ok.....

Eric X. Per. 3 TA said...

I have the Algebra book at home, but I'm too lazy to pull it out.

Natasha L Per.4 TA said...

psh Eric.... and where did you happen to get that from?

MLYHOOPS said...

he prob bought it.... anywway can anyone help on number 11?

using the addition method
4x-5y=7
-4y+5y=7

i dont get it.... if u add them together it would be 0=14....? so im confused

Unknown said...

Do we need justifications?

JonathanK.per.3 said...

Today in math class i got kicked out but i stilled learned new methods such as the elimination method and we also collected homework and went over questions...

JonathanK.per.3 said...

x+y=5
2x-y=4


3x =9
1/3(3x)=1/3(9)
=
x=3

JonathanK.per.3 said...

Also...
2x-y=4
2(3)-y=4
6-y=4
________
-6 -6

-y =-2

_______
-1 -1
y=2

(3,2) is the solution

MLYHOOPS said...

haha jonathan!!!!!

Sean K Per.3 TA said...

Period 2:
Period 3: Jonathan K.
Period 4:
Period 5:
Period 6: Marcus B.

@Matthew, If you put both equations into slope-intercept form, the you get:
y=4/5x+7
y=4/5x+7
Since they are the same line, then there are infinitely many solutions. This happens in most, if not all, situations that are like yopur example. Test just to make sure and show work.

Eric X. Per. 3 TA said...

umm..Sean, it's actually y=4/5x-7/5 and y=4/5x+7/5.
These lines are parallel, and thus, never intersect, so there are no solutions.

When you get 0=0, 5.678=5.678, then there are an infinite number of solutions.

When you get 0=5.6819294859, then there are no solutions.

MarcusC Per6 said...

After going over some questions from last night's homework, Mr. Gerson showed us how to use the Elimination Method to solve problems.

Example:
x+y=10
4x-y=8
---------
5x=18
1/2(6x)=1/2(18)
1x=3
x=3

x+y=10
(3)+y=10
3+y=10
-3 -3
---------
y=7

Final Answer:(3,7)

Easy as 3.14159!

Natasha L Per.4 TA said...

~Journal Entries~

Period 2:
Period 3: Jonathan K.
Period 4:
Period 5:
Period 6: Marcus B. Marcus C.

^ Must be a coincidence right?

MLYHOOPS said...

@sean thnx but i got it.... i was just not paying attention to my work and i wasnt focused but once i was i figured out everything simply... haha

MLYHOOPS said...

@natasha.. idk maybe?

Sean K Per.3 TA said...

@Eric Oh sorry I forgot to divide the 7s. :P Hope I do better in MATHCOUNTS.