Question

Solve the system 5x+7y=16(21y-15x=-48)

Answer 1

Ummmmm its 5x+7y=16
-21y-15x=-48

Answer 2

oh ok

Answer 3

7y + 5x = 16
-21y - 15x = -48
------------------
21y + 15x = 48
-21y - 15x = 48
=============
0 + 0 = 0

Answer 4

so what would it be?

Answer 5

Im confused I thought you suppose to add like terms together

Answer 6

that's substitution method

Answer 7

I used elimination method

Answer 8

well it is too complicated to use the substitution method because if you do there will be too many fractions so I used the elimination method which will eliminate the x or y.

Answer 9

Oh i really dont know the elimination method

Answer 10

oh you didn't learn that yet?

Answer 11

ok if you didn't Ill teach you

Answer 12

No sorry. My teacher never taught us that

Answer 13

ok there are 2 types of methods substitution and elimination method

Answer 14

you already know the substitution method right?

Answer 15

Sort of

Answer 16

ok if you are confused do you have any other problem you don't get? so we can use that as an example?

Answer 17

5x+7y-2z=16
2x+3y-3z=4
-2x-8y-4z=15

Answer 18

is that one whole question?

Answer 19

Yeah i have to solve for x,y,and z

Answer 20

ok lets see we cannot use substitution on this one so lets use elimination method.

Answer 21

ok

Answer 22

well maybe we can

Answer 23

but will take a very long time

Answer 24

Well sorry but we cannot use elimination method

Answer 25

we will use substitution

Answer 26

ok

Answer 27

We will find the X first
5x+7y-2z=16
2x+3y-3z=4
-2x-8y-4z=15
-------------------
5x + 7y - 2z = 16
y = -2/3x + z + 4/3
y = -2/8x + -4/8z + -15/8
---------------------------
so we plug it into the equation of 5x + 7y - 2z = 16
1.) 5x + 7(-2/3x + z + 4/3) = 16
2.) 5x + 7(-2/8x + -4/8z -15/8) = 16
--------------------------------
we are going to multiply The first equation by 3 so we can get whole numbers instead of fraction
1.)5x - 14/3x + 7z + 28/3 = 16
15x - 14x + 21z + 28 = 48
--------------------------
x + 21z + 28 = 48
x + 21z = 20
x = -21z + 20
-------------------
we found the x so we plug it into the x from the beginning of the equation
5x+7y-2z=16
5(-21z + 20) + 7y - 2z
-105z + 100 + 7y - 2z = 16
-107z + 7y = -84
7y = -107z - 84
y = -107/7z - 12
-----------------------
plug in the x and the y into the equation
5x+7y-2z=16
5(-21z + 20) + 107z - 12 - 2z = 16
-105z + 100 + 107z - 12 - 2z = 16
z = no solution
x = -21z + 20
y = -107/7z - 12

Answer 28

that was a lot of work

Answer 29

Yeah thanks for the help on this one. I have another on like this so now i will be able to handle it.

Answer 30

ok

Answer 31

good luck

Answer 32

thanks