Question

Solve
4x + y + z = 1
8x – 4y – 7z = 2
5y + 9z = 3
Help?

Answer 1

Matrix!

Answer 2

Do you know how to set this up as a matrix..?

Answer 3

luigi!!!!

Answer 4

Yes?

Answer 5

I don't even have a clue @Luigi0210

Answer 6

Matrix form is the same as equation form.. just without the variables.

Answer 7

I'd use the first two equations to eliminate x. Then use the new equation with only y and z with the third equation to solve for y and z.

Answer 8

math is my dumbest point so i had seeing numbers put together like i broke my keyboard kuz i hate numbers

Answer 9

Wait, do you know how to use matrices yet? @acacia

Answer 10

Multipy both sides of the first equation by 2, then subract the left side of equation 2 from its left side, and E2's right side from E1's right side:

8x + 2y + 2z - 8x - (-4y) - (-7z) = 2 - 2
6y + 9z = 0
6y = -9z
y = -1.5z

Substitute that for "y" in E3:

5 * (-1.5z) - 9z = 3
-7.5z - 9z = 3
-16.5z = 3
z = –3/16.5 = –6/33 = –2/11

And "y" comes from y = –1.5z = (–1.5)(–2/11) = 3/11

And put that back into E2:

8x - 4(3/11) - 7(–2/11) =2
8x - 12/11 + 14/11 = 22/11
8x + 2/11 = 22/11
8x = 20/11
x = 20/88 = 5/22
This is how my answer is turning out and I don't know if its right, it looks wrong to me

Answer 11

@Luigi0210 sorta, kinda I'm a slow child

Answer 12

4x + y + z = 1
8x – 4y – 7z = 2
5y + 9z = 3

Multiply the first equation by -2
Write the second equation below it
Then add the two equations

-8x - 2y - 2z = -2
8x - 4y - 7z = 2
-------------------
-6y - 9z = 0

Now you have a new equation in only y and z. Solve it together with he third equation, which only has y and z.

-6y - 9z = 0
5y + 9z = 3

@acacia Can you handle a system of 2 equations in 2 unknowns?

Answer 13

Hint: Add the two equations together. That will eliminate z, so you can find y.

Answer 14

so then would it be y=-3? @mathstudent55

Answer 15

-6y - 9z = 0
5y + 9z = 3
------------
-y = 3
y = -3
Correct!

Answer 16

I feel like I just made a break through!(:

Answer 17

@mathstudent55 can you help me with another one?

Answer 18

That is what I was about to ask would I have to do it the same way I solved for y?

Answer 19

Now that you have y, use an equation that has only y and one more variable to find the other variable. Use equation 3:
5y + 9z = 3
Since y = -3, you get:
5(-3) + 9z = 3
Solve for z.

Answer 20

Once you also have z, then you can use the first equation. Plug in y and z, and solve for x.

Answer 21

okay so z=2 right?
@mathstudent55

Answer 22

and the the last one would be 0.5? If i'm right

Answer 23

Correct.
Good work.

Answer 24

but wait for my multiple choice answers it has

A. (0.5, -3, 2)
B. (1, 2, 3)
C. (-3, 0.5, 2)
D. (0.5, 3, 2)
aren't A and C the same?