Author Topic: Algebra Question (Read 5511 times)

MrMxyzptlk · « **on:** May 11, 2009, 11:39:29 AM »

Okay, I'm about to have an argument with another Math teacher here....

Factor this polynomial for me:

3y² + 22y - 18

jim360 · « **Reply #1 on:** May 11, 2009, 11:55:23 AM »

Solving the quadratic equation 3y²+22y-18=0 gives y₁ = (-22+ (484+216)^1/2)/6 = (-22 + 700^1/2)/6

Then y₂ = (-22 - 700^1/2)/6. That seems right.

Numerically these are roughly: y₁=0.7429 and y₂=-8.07625.

SO to answer your question, 3y²+22y-18= (y-0.7429)(y+8.07625)

MrMxyzptlk · « **Reply #2 on:** May 11, 2009, 12:13:24 PM »

Um, I should've mentioned this: it's intermediate algebra... all answers are whole integers, e.g. (y - 3) (3y + 6) , which actually is 3y² - 3y - 18 , or (3y - 3) (y + 6) which is 3y² + 15y - 18 ....

( But I think you've just proven my point for me, TYVM!

)

MrMxyzptlk · « **Reply #3 on:** May 11, 2009, 12:50:55 PM »

You guys are reinforcing my position: I think she copied the problem over incorrectly on her tests....

I think it was supposed to be: 3y² + 15y - 18 . . .

She'll have nothing to do with my input, tho, despite my asking her to produce the proof herself....

(I've also suggested to her that she call it a "trick question" and accept "3y² + 22y - 18" as a correct answer!

)

jim360 · « **Reply #4 on:** May 11, 2009, 12:54:58 PM »

Well once I came up with my answers I ran it through a polyhnomial solver to see what it came up with - guess what? the same numbers. You can show her the full iterated solution if you like...

MrMxyzptlk · « **Reply #5 on:** May 11, 2009, 01:00:47 PM »

Thx. I'll paraphrase what's been said here and leave it in her mailbox today, but I don't think it will change anything....

(I wonder how long that test has been passed down from teacher to teacher like that, or where along it's chain of life it got mangled up?? )

...Consider this topic "closed!"

Thx again!

Soz 0wned U · « **Reply #6 on:** May 11, 2009, 10:43:47 PM »

Adding something; Since when did you go to school mxy?

Did you repeat the 8th grade about 40 times?

BFM_Hydra · « **Reply #7 on:** May 11, 2009, 10:53:44 PM »

Mxy is an English teacher

MrMxyzptlk · « **Reply #8 on:** May 13, 2009, 05:46:14 PM »

Quote from: BFM_Hydra on May 11, 2009, 10:53:44 PM

Mxy is an English teacher

English, Science, and Technology, and I'm qualified to teach Math, but they already have a more senior Math teacher where I am....

TYVM!

BFM_Hydra · « **Reply #9 on:** May 13, 2009, 05:47:25 PM »

Eh, close enough!

BFM_Edison · « **Reply #10 on:** May 14, 2009, 02:13:02 PM »

Yet this math teacher can't do math

MrMxyzptlk · « **Reply #11 on:** May 14, 2009, 05:25:31 PM »

Quote from: bfm_Edison on May 14, 2009, 02:13:02 PM

Yet this math teacher can't do math

Hunh?

jim360 · « **Reply #12 on:** May 14, 2009, 05:32:33 PM »

I believe that my esteemed colleague refers to the teacher with whom you are having this algrebraic dispute.

YOu've so got to tell us what happens Mxy!!!

MrMxyzptlk · « **Reply #13 on:** May 14, 2009, 05:47:25 PM »

Quote from: BFM_three60 on May 14, 2009, 05:32:33 PM

I believe that my esteemed colleague refers to the teacher with whom you are having this algrebraic dispute.

YOu've so got to tell us what happens Mxy!!!

Oh I most certainly WILL!

(Patience, tho, pls! We only meet weekly with students here....)