Question

I need help ASAP (Elimination method)
Not looking for just answers! I would like someone to work it through with me if possible!


Use ELIMINATION method to solve:
(x/2+y/3=7/5),(2x/3+3y/4=5/4)

Answer 1

Ok just a moment I'll try to help you

Answer 2

It would be easier if you get rid of the fractions by multiplying the equations throughout by the LCM.

Answer 3

Yep it would

Answer 4

So 12 for both?

Answer 5

No. You'll have to go to 60 to get them all!

Answer 6

@tkhunny ok ill do that hold on plz!

Answer 7

30 times the first equation
12 times the second equation

Answer 8

30 times the first equation: 15x + 10y = 42
12 times the second equation: 8x + 9y = 15

Pick which variable you want to eliminate.

Answer 9

@aum do you mean like this?

Answer 10

No you are multiply the top by 30 and the bottom also by 30.
But in an equation we can multiply the equation THROUGHOUT by any number and the equation will still be valid.
For example, the equation, 2x = 4 remains the same if we multiply throughout by 5:
10x = 20 is same as 2x = 4. In both cases x = 2.

So multiply the first equation throughout just by 30 because the least common denominator of 2, 3 and 5 is 30.

Answer 11

Multiply the second equation throughout by 12 because the least common denominator of 3, 4 and 4 is 12.

Answer 12

The reason we are multiplying is to get rid of the denominator and so the equations become easier to work with.

Answer 13

Sorry I am like really confused.. isn't that what I did?

Answer 14

\(\Large 30 * \frac x2 = 15x \)
What you are doing is: \(\Large \frac{30}{30} * \frac x2 = \frac{30x}{60} \)

Answer 15

ohhh ok so I am only multiplying the top! okayyy, hold on plz lol

Answer 16

so like this?

Answer 17

You got the LHS of both equations correct. But RHS of both are incorrect.

Answer 18

What is RHS?

Answer 19

RHS - Right Hand Side
LHS _ Left Hand Side (of equations)

Answer 20

ohh ok cool. so the 8x+9y=5 is incorrect?

Answer 21

15x + 10y (the LHS) is correct. = 35 (RHS) is wrong.
8x + 9y (the LHS_ is correct. = 5 (the RHS) is wrong.

Answer 22

\(\large \frac 75 * 30 = 42\) (not 35)

\(\large \frac 54 * 12 = 15\) (not 5)

Answer 23

oh lol im so dumb! Ok now I see what i did wrong! So i am going to finish the problem and ill post what i got and would you mind telling me if I did it correctly??

Answer 24

sure.

Answer 25

So either I am just reallllllly bad at math or I did something wrong... or just both ...
@aum
this is what I got but my math book says the answer is (3,-1) and I didn't get that...

Answer 26

You may have made a mistake in the numbers in the original problem posting.
Can you post a screenshot of the question?

Answer 27

yep

Answer 28

y = -111/55 is CORRECT for this problem as it appears in the original posting. (BTW, the last line in your answer should be y = -2.01 and not x = -2.01 ).

Answer 29

Will you be posting a screenshot of the question?

Answer 30

Oh ok lol ! an it is attached to this

Answer 31

http://assets.openstudy.com/updates/attachments/53fd2bade4b0eb771de5a026-santanag-1409104929185-photo10111.jpg

Answer 32

The mistake in your original posting is, the RHS of the first equation should be 7/6 and not 7/5.

Answer 33

Ohhhh omg Sorry lol!! well at least I know how to do it now! So instead of multiplying by 30 I would do it by 6?

Answer 34

correct. I will do it below from start to finish.

Answer 35

x/2 + y/3 = 7/6 (multiply by 6)
3x + 2y = 7 ----- (1)

2x/3 + 3y/4 = 5/4 (multiply by 12)
8x + 9y = 15 ----- (2)

8 x (1): 24x + 16y = 56
-3 x (2): -24x - 27y = -45
add
-11y = 11
y = -1
put it in (1)
3x + 2(-1) = 7
3x - 2 = 7
3x = 9
x = 3

x = 3, y = -1 or (3,-1)

Answer 36

Awesome!!! Thank you so much for taking the time to work the problem out with me!

Answer 37

You are welcome. :)