posted by .

x+y=1
y-z=-3
2x+3y+z=1

This can be solved a number of ways.
1) subsitition
2) determinants
3) matricies.

Substution:
x= 1-y
y= z+3 or x= 1-z-3

In the third equation , put those two things for x, and y.
2x+3y+z=1
then solve for z. Then go back and solve for x and y.

I've done that already such as
the book states the following
how did they get there after adding equation 2 and three

Substitute x = 1-y and z = y+3 in the third equation. Then you get an equation in y only:
2(1-y) + 3y + (y+3) = 1
2y + 5 = 1
y = -2
Then use the equations for x and z again.
x = 1-(-2) = 3 etc.

## Similar Questions

1. ### math

How do i solve inequalitites with three variables. I still can't figure it outplease help. x+y=1 y-z=-3 2x+3y+z=1

How do i solve inequalitites with three variables. I still can't figure it outplease help. x+y=1 y-z=-3 2x+3y+z=1 Where are the inequalities?
3. ### a.p. calculus help please!

My a.p. calculus teacher doesn't know how to do this problem (like many others) so he's giving us 5 points extra credit on our test if we can figure it out, but I don't know how to do it: It's as the lim-->infinity (x+sinx)/(x+cosx) …
4. ### TO DRWLS/MATH HELP PLEASE

How do i solve inequalitites with three variables. I still can't figure it outplease help. x+y=1 y-z=-3 2x+3y+z=1 THE ANSWERS ARE X=3,Y=-2,Z=1 i KNOW THE ANSWERS I JUST DON'T KNOW HOW THE BOOK GOT THE ANSWERS . i 'VE TRIED MANY DIFFERENT …
5. ### to annonymus can you help me with math

How do i solve inequalitites with three variables. I still can't figure it outplease help. x+y=1 y-z=-3 2x+3y+z=1 the answers are 3,-2,1 how do get there by solving linear equations with three variables. 5x-2y-z=2 -y+2z=11 x+y+z=-3
6. ### Basic Math

I forgot how to solve for two variables... Please check if I solved both problems properly! Thank you. Equations: (solve for t and z) 12t + 4z = 80 2t + 4z = 20 My answer: t = 2, z = 14 The steps: (simplified it) z = 20 - 3t, z = 5 …
7. ### Algebra

I was given this problem to solve and no matter what order I multiply the variables I don't get the right answer. 27xy, when x=12.7 and y=100.4 the answer is 34,427.16 I cannot figure out the way to achieve this answer. I find problems …
8. ### Precalculus

I asked this yesterday but I was told my answer was incorrect by my professor. ln x^5 - ln x^2 = 3 solve for the unknown. I have reviewed my Log laws but yet I still cannot figure out what the answers are. The question asks for me …