help please!!!?

Question

i hate math so i dont understand any of the algebra stuff....can you help me understand how to do this....
solve the system by elimination method:4x + 3y=13
3x - 3y=15
and then theres this one....
solve the system by subsitution:2x + y=9
3x +5y= -11

im not trying to get people to do my homework its just i have to study this for a test tomarrow and i am trying to prove to my dad that i will get a good grade...i just dont understand this...sorry..

Answer 1

Ok. In the elimination method, you have to *eliminate* one of the variables. Let's take the first set.

4x + 3y = 13
3x - 3y = 15

Add both equations. Since +3y and -3y are opposites, they will cancel out. You end up with:

7x = 28

This part is easy. Divide both sides by 7 to isolate the variable. This will give you a value for X.

Now to find the value of Y. Substitute the value of X into one of the equations. Work it out, and you will find your answer.
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The second problem is easier.

2x + y = 9
3x + 5y = -11

As you can see, Y is by itself in the first equation; it doesn't have a coefficient. Move 2x to the other side of the equation by changing its sign. You'll end up with:

y = 9 - 2x

Plug this equation into the second part of the set, replacing the original "y." You will come up with:

3x - 5(9-2x) = -11

Work this out, and you'll find out what X equals. Use this value of X in the first equation. It will then give you the exact value of Y.
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***Well, I hope I helped you!***

Answer 2

1st one:
adding the two equations gives you:

4x + 3y = 13
+ 3x -3y = 15
-------------------------
7x = 28
x = 28/7 = 4
4(4) + 3y = 13

3y = 13 - 16 = -3 so y = -1

for the 2nd one:
solve for y in terms of x;
y = -2x + 9

substitute y into the 2nd equation.

3x + 5(-2x+9) = -11

3x + -10x + 45 = -11

-7x =34

x = -34/7;

now sub in -34/7 for x to solve y

-2(-34/7) +9 = y

68/7 + 9 = y

Answer 3

your textbook should show u

add 3x-3y=15 and 4x+3y=13 together since -3y and +3y are opposite they cancel out
then you will get
7x=28
solve for x then plug it in to the original equation to get Y



for substitution solve for one variable
for ex. 2x+y=9 now is Y=9-2x
now plug the 9-2x into the other equation for Y
so itll be 3x+5(9-2x)= -11
FOIL the 5(9-2x) part and you can figure it out from there

good luck

Answer 4

its a simple question....
4x+3y = 13
3x-3y = 15
3y cansels so ur left with 4x=13 & 3x = 15 combined them ....
4x = 13
+ 3x = 15
_________
add them straight down.... now just divide your answer on your right by your the number the answer in front of x.... and you get x...now plug in x in any of the equations and solve for y...remember to make sure your x answer and y answer fits into both your equations if it doesn't you probably added wrong...for the second one its almost the same thing except your substituting....
re write....2x + y = 9 so that y is by itself and then just substitute your answer into the y for 3x + 5y = -11 hint it should look something like thist 3x + 5 (9-2x) = -11

Answer 5

4x+3y=13
+ 3x-3y=15
-------------
7x =28
(y cancels )
x=4
4x+3y=13
4(4)+3y=13
16+3y=13
3y=-3
y=-1

2x+y=9 = -y=-2x+9 = y=2x-9
3x+5y=-11
(sub 2x-9 for y into 2nd equation)
3x+5(2x-9)=-11
3x+10-45=-11
3x-35=-11
3x=-11+35
3x=24
x=8

2x+y=9
2(8)+y=9
16+y=9
y=-7

Answer 6

for some odd reason i think your trying to get me to do your homework... w/e 3x - 3y = 15 hmm....its impossible to solve since i dont know what the varriables stand for. sorry!

Answer 7

Uh,y`see it`s very simple.Now we know 4+3doesnt =13.Whatx plus what x3 when added togther =13.4x1=4,stay with me,and
3x3=9,4+9=13!!!!x=1,y=3.got it????Yer on ter own,I`m tired.

Answer 8

3x - 3y=15
x= 8
y=3

Answer 9

I admire everyone that is helping you, because on I have never been very good. Hope everyone helps you so that you can study.pu

Answer 10

Jesus doesn't want you to do math. Seriouisly, if he did, he would have made it easy for you.