Question

If you were to use the substitution method to solve the following system, choose the new system of equations that would result if x was isolated in the second equation.

3x + y + 2z = 1
x + 2y – z = –8
3x – y – 3z = 18

Answer 1

x = -8 -2y +z

Answer 2

7y – z = 25
5y – 6z = 42

–5x – 5z = –10
6x – z = 19

7x + 3z = –10
–5z = 19

–5y + 5z = 25
–7y = 42

Answer 3

those are my options A,B,C,D

Answer 4

Cool, I'm not done yet.

Answer 5

@johnweldon1993 Please take over. Got to go.

Answer 6

thankyou anyway @primeralph :)

Answer 7

So isolate 'x' in that 2nd equation

x + 2y – z = –8

subtract 2y and add z to both sides to isolate x

x = -2y + z - 8

Now when you substitute that into the other 2 equations you get


3(-2y + z - 8) + y + 2z = 1
3(-2y + z - 8) – y – 3z = 18

simplified down we get

-6y + 3z - 24 + y + 2z = 1
-5y + 5z - 24 = 1
-5y + 5z = 25

And

-6y + 3z - 24 - y - 3z = 18
-7y - 24 = 18
-7y = 42

So those 2 again are

-5y + 5z = 25
-7y = 42

Look familiar? :)

Answer 8

Thankyou so much so answer is D :)

Answer 9

That is correct! :)