+0

+2
386
16
+2448

I tried solving these but I gave up lol I could only get to the parts where you add the x values and add the y values

For example, for number 1, 7x+-14x=-7x and 2y-3y=-1y (you would only add if there is a + right?)

And then add -10+29= 19 so I got to -7x+-1y=19 but i don't even know if I did that right. I got stuck there.

Aug 28, 2018

#1
+100516
+4

The keys to  solving  these

(1)  line up all variables  on  one side of the equation and constants on the other

(2)  pick a variable to eliminate....either will do....this is the REAL key

(3) not a necessity...but I always like to get rid of fractions, too, before  I start

7x + 2y  = -10

-14x  - 3y  = 29

I see that if I multiply the top equation by  2 and add it to the second equation,  the "x" term will disappear..so

14x  + 4 y  = -20

-14x - 3y  = 29    add these  and we get

y  = 9

To find x...we can  use any equation...so...

7x + 2(9)  = -10

7x + 18  = -10

7x = -28

x  = -4

So.....(x, y)  =(-4, 9)

Do you want to try a couple on your  own, RainbowPanda  ??

Aug 28, 2018
edited by CPhill  Aug 28, 2018
#2
+4221
+2

@CPhill, 29 or -29? This was in step 2.

(2) Multiply the second equation by 2, so: -9x-14y=-29, 10x+7y=-2, -9x-14y=-29, 20x+14y=-4..

So, adding: y gets canceled, and 11x=-33, \(x=-3\), so y= -9(-3)-14y=-29, 27-14y=-29, 14y=27+29, 14y=56, \(y=4.\)

Aug 28, 2018
edited by tertre  Aug 28, 2018
edited by tertre  Aug 28, 2018
edited by tertre  Aug 28, 2018
#3
+100516
+2

Sorry.... typo...should be 29....

CPhill  Aug 28, 2018
#4
-2

Nobody is going to help you. You should probably pay more attention in class. I guess that means you're kind of dumb. πΈπ°ππππ©.

Can you answer me this, what is 2+6578901+51784946% and -17264967+-837956881868078.

Aug 28, 2018
#7
+100516
+3

Well, Guest.....maybe everyone isn't as brilliant as you are...besides....this elimnation stuff isn't that easy when you're new to  it....

CPhill  Aug 28, 2018
#5
+100516
+2

4)  -20  + 10 x  = -10y

45  = 6x  - 27 y

Rearrange each as

10x  + 10y   = 20

6x  - 27 y  = 45

I see that I can divide the top equation  by 10  and the bottom by 3  to  get :

x + y  = 2

2x - 9y  = 15

I see that I can  eliminate  'x"  by multiplying the top equation by  -2

-2x - 2y  = -4

2x - 9y  = 15     add these

-11y = 11

y = -1

And using any equation to find x, we  have

x + y  = 2

x + (-1)  = 2

x - 1  = 2

x  =3

So  (x,y)  =  (3 , -1)

Do these steps help  ???

Aug 28, 2018
#6
+4221
+3

(4) Hint: Try to rearrange the equation, the first and second: Take -10y to the other side, and see what you can do.

Aug 28, 2018
#8
+100516
+2

Thanks, Tertre  !!!!

CPhill  Aug 28, 2018
#9
+4221
+2

Welcome, CPhill!

tertre  Aug 28, 2018
#10
+2448
+2

Thank you so much for your help, both of you. I have tried it and yet i'm still too dumb to solve these. >.<

Aug 28, 2018
#11
+100516
+3

You're not  "dumb"....it's just hard to  get the hang of this...

I'll do   2)  and  3).....maybe that will help some

2)  - 9x  - 14y   = -29

10x + 7y  =   -2

Ok....do you see that we  can  eliminate y  by  multiplying the second equation by -2  ??...so we have

-9x - 14 y  =  -29

20x  + 14y  = -4     add these

11x  = -33   divide by 11

x  = -3

Using  10x + 7y   = -2 to find y, we have

10(-3) + 7y  = -2

-30  + 7y = -2    add 30  to both sides

7y  = 28   divide by 7

y  = 4

So...(x, y)  = ( -3, 4)

CPhill  Aug 28, 2018
#12
+100516
+3

3)   0 =  -36x + 14y  + 8

0 =  18y  - 9  - 27x

Rearrange these as

36x - 14y  = 8

27x  - 18 y   = -9

Divide the first equation through by 2  and the second one through  by 9

18x  -  7y   =  4

3x   -  2y   =  -1

I see that we  can  get  "-18x"  by multiplying the second equation by  -6  ...so we have

18x - 7y   =  4

-18x + 12y  = 6    add these

5y  = 10    divide by 5

y  = 2

Using   3x  - 2y  =  -1   to find x, we have

3x  - 2(2)  = -1

3x  - 4  =  -1

3x  = 3   divide by 3

x  = 1

So  (x,y)  = ( 1, 2)

Aug 28, 2018
#14
+2448
+3

It's just that some of the problems are different so it makes it harder to understand and to know you are doing the problems correctly because you can't go off of one problem if they are even the slightest bit different. Am I even making sense right now xD

Thank you for helping~

RainbowPanda  Aug 28, 2018
#15
+100516
+1

Yep...that is what makes this a little difficult...there  isn't a "cookbook"  method of doing these....

Don't worry...you will get the hang of it....!!!!!

Just practice a few...

CPhill  Aug 28, 2018
edited by CPhill  Aug 28, 2018
#16
+2448
+1

Problem is there is also other ways of solving these problems like solving the system of equations by substitution and of course elimination.

RainbowPanda  Aug 28, 2018
#13
+814
+3

For (3). Just take the constant to the other side, you're left with x and y= constant.

Here, I'll show you!

0=-36x + 14y + 8

0 = 18y -9 -27x

Best thing to do first: 36x - 14y = 8 - 0, 36x - 14y = 8

And, for the second equation: 27x - 18y = 0+9, 27x - 18y = -9.

Now, divide the first equation by 2 and the second equation by 9, because the x will end up as a canceling factor.

So, 18x-7y=4, 3x-2y=-1, try to make both x's equal, subtract find x, then solve for y!

Aug 28, 2018