Thread: x - 3(2x +3x) = 8 - 5x

Help me out here.

x - 3(2x + 3) = 8 - 5x

This is really a simple problem, I remember doing things like this one all the time but I forgot what I was supposed to do.

x - 6x - 9 = 8 - 5x
-5x - 9 = -5x + 8
-17 = 0

So then it becomes the same equation except with a different y intercept...


I don't know what went wrong. I remember getting problems with an answer like this but I forget how to do it. My first instinct is just to say x is undefined, or no solution but... I dunno.

So no solution or undefined?

Uh, your solving it incorrectly Pull all of x on one side, and all numbers on the other. You end up getting the same result, but it's easier.

0x = 17

x is undefined.

Ty.

This is a really poorly stated question if that's how it was given. This should actually have been given as the intersection of the lines y = -5x -9 and y = -5x - 8. Looking at it that way, it's obvious, without doing the math, that there is no solution, because the lines are parallel.

Oh, it was a line intersect problem I hate y=mx+b format, I prefer parametric equations.

Originally Posted by drewmandan

This is a really poorly stated question if that's how it was given. This should actually have been given as the intersection of the lines y = -5x -9 and y = -5x - 8. Looking at it that way, it's obvious, without doing the math, that there is no solution, because the lines are parallel.

agreed that is why I put it as -5x -9 = -5x - 8 when I was writing it but I felt like I was missing something.

So is undefined and no solution the same thing btw? I feel like a moron but I haven't taken math in a few months.

Let the record show...that I fucking hate math.

That is all.

Carry on.

Originally Posted by Oneironaut

Let the record show...that I fucking hate math.

That is all.

Carry on.

Me too... but im good at it

I forgot all about those funky techniques I learned in high school.

But doing it the hard way (by head, like counting (yea counting didn't completely die out in the 1950s, unfortunately),

And

0 seems to be the answer to x.

Originally Posted by Sandform

agreed that is why I put it as -5x -9 = -5x - 8 when I was writing it but I felt like I was missing something.

So is undefined and no solution the same thing btw? I feel like a moron but I haven't taken math in a few months.

No, they're not as far as I know. Undefined is when you divide by zero, and no solution is when a system is inconsistent (linear algebra term).

Originally Posted by Neruo

0 seems to be the answer to x.

Wrong. There is no solution.

Originally Posted by capoopy

Me too... but im good at it

Yeah, I hate that. Im actually very good at math but the only thing I like about it is set theory and logic and some of analysis and calculus, perhaps gemoetry. Probability theory and statistics and all that jazz I totally hate.

I ehat hmat.

x^3-3x^2-x+3=0

Originally Posted by Sandform

I ehat hmat.

x^3-3x^2-x+3=0

Factor theorem.

x=-1 is a factor. Now do some long division to get

(x+1)(x^2 -4x +3) = 0
(x+1)(x-3)(x-1)=0

solutions are x=-1, 1, 3

Why is x=-1 a factor?

Well that is to say...is x=-1 something you just look for in a situation like this or is there some method to deciding that it is x=-1