Question

The following system is solved by substitution. Which expression is substituted for z in the second and third equations?

x + 4y + z = -10
3x - 3y + 6z = -21
x + 2y + 2z = -10

a. x + 4y - 10
b. -x + 4y - 10
c. -x - 4y - 10
d. x - 4y - 10

Answer 1

You know how to do this....quit playin....

Answer 2

Hint...solve for z in the first equation....

Answer 3

I actually don't. Every time I do these equations it comes out as wrong :/ I have no idea why. I normally really good at stuff like this -- this entire unit has thrown me off. My grade has gone from a 95 to a 91 because of this unit x_x

Answer 4

This is the last work I have to do for it, though. So I won't be bothering anybody with questions like these after tonight.

Answer 5

Wow, you're still in the 90s...you're not doing bad at all..

Answer 6

Hey, some of the best times of my life were in the 90s....

Answer 7

Yeah, but I need a ninety for this class if I want to get into Honors Precalc and AP Calc, baha. Normally I don't struggle this hard for my nineties.

Har, har, very funny :P I was still in diapers, so I can't really say they were the best times. Though, it is nice having everything taken care of like that.

Answer 8

If you think earning an A in Algebra is hard...wait until you get to Honors Pre-Calc and AP Calc...

Answer 9

Anyways, I'm pretty sure you've found the expression for z by now Smart girl....

Answer 10

Right?

Answer 11

Okay, I know you may be panicking right now but don't worry.

To solve for z in the first equation, simply subtract x and 4x from both sides in the first equation. Let me know what you get.

Answer 12

I tried solving and got:

-3x - 27y = 39
3x + 2y = -9\

Needless to say, I really don't thikn that's right x_x

Answer 13

And sorry the repsonce is so late -- I had to finish some laundry up.

Answer 14

What the.....

You were ONLY supposed to be solving the first equation ONLY for z.

Answer 15

How did you get that?

Answer 16

OH, crap. I thought that they asked to substitute in the equation in the second two as well. Nevermind. I DO know how to do this. I'm so sorry. Oh, god. I'm so dumb. I didn't read that through the first time.

... /embaressed.

Answer 17

So when I said, "Hint, solve the first equation for z"....how did you interpret that? Oh..nevermind it doesn't even matter now, lol

Answer 18

If I was substituting in, I WOULD solve for Z first then substitute i the second two equations :P And that's always what trips me up -- substituting in and trying to solve.

Answer 19

Well, the way I solve these, I don't think anybody would do it the way I do it....