« previous next »
Pages: [1]

Author Topic: Sophomore Math Problem has me stumped  (Read 3749 times)

Stetson

  • friends
  • Senior Member
  • ***
  • Posts: 1,094
Sophomore Math Problem has me stumped
« on: January 07, 2011, 06:00:15 PM »
Factor the trinomials:  Should have 2 sets of ( ).

4x^2 - 3x + 7

We have it down to 28:  (4x  ) (4x  )  but cannot find the number that adds up to -3 and multplies to 28.  We came up with 7 and 4 but with the -3 we can't find anything that fits.

Any help?

Report to moderator   Logged

AZRedhawk44

  • friends
  • Senior Member
  • ***
  • Posts: 13,990
Re: Sophomore Math Problem has me stumped
« Reply #1 on: January 07, 2011, 06:16:03 PM »
I can come up with factors for:

4x^2 +3x - 7 = (x - 1)(4x + 7)

But I can't find any for 4x^2 -3x + 7.

To get the positive third element, both factors must have the same sign for the constant.  And it has to be 1 and 7 since 7 is prime.  

Sure you didn't copy the problem incorrectly?
Report to moderator   Logged
"But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."
--Lysander Spooner

I reject your authoritah!

dogmush

  • friend
  • Senior Member
  • ***
  • Posts: 14,089
Re: Sophomore Math Problem has me stumped
« Reply #2 on: January 07, 2011, 06:16:29 PM »
Are you sure of the problem?

Unless my Quadratic formula is failing me that equation has no real solutions.

(b^2-4ac is a negative number)
Report to moderator   Logged

AZRedhawk44

  • friends
  • Senior Member
  • ***
  • Posts: 13,990
Re: Sophomore Math Problem has me stumped
« Reply #3 on: January 07, 2011, 06:24:45 PM »
http://www.algebrahelp.com/calculators/expression/factoring/calc.do?expression=4x^2+-3x+%2B+7

Already factored.

Versus:

http://www.algebrahelp.com/calculators/expression/factoring/calc.do?expression=4x^2+%2B3x+-+7

This came up with:

(-7 + -4x)(1 + -1x)

I came up with:

(x - 1)(4x + 7)

If you multiply each factor by -1 (remember, -1^2 = 1) of the online tool, you get:
(7 +4x)(-1 + x)
reorder:
(4x + 7)(x - 1)

I don't know why the tool got my answer inverted by -1 squared, but I'm mildly pleased I can still factor after having not done it for 15 years. =D
« Last Edit: January 07, 2011, 06:35:44 PM by AZRedhawk44 »
Report to moderator   Logged
"But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."
--Lysander Spooner

I reject your authoritah!

AZRedhawk44

  • friends
  • Senior Member
  • ***
  • Posts: 13,990
Re: Sophomore Math Problem has me stumped
« Reply #4 on: January 07, 2011, 06:29:49 PM »
Quote from: dogmush on January 07, 2011, 06:16:29 PM
Are you sure of the problem?

Unless my Quadratic formula is failing me that equation has no real solutions.

(b^2-4ac is a negative number)

That's to find the position where:

ax^2 + bx + c = 0.

The function never intersects with zero.  So the quadratic formula has no use, other than to tell us that the function never equals zero.

Quadratic formula isn't used for factoring.
Report to moderator   Logged
"But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."
--Lysander Spooner

I reject your authoritah!

Jamisjockey

  • Booze-fueled paragon of pointless cruelty and wanton sadism
  • friend
  • Senior Member
  • ***
  • Posts: 26,580
  • Your mom sends me care packages
Re: Sophomore Math Problem has me stumped
« Reply #5 on: January 07, 2011, 07:27:20 PM »
I taste purple.
Report to moderator   Logged
JD

 The price of a lottery ticket seems to be the maximum most folks are willing to risk toward the dream of becoming a one-percenter. “Robert Hollis”

dogmush

  • friend
  • Senior Member
  • ***
  • Posts: 14,089
Re: Sophomore Math Problem has me stumped
« Reply #6 on: January 07, 2011, 07:35:22 PM »
Ah yes, well it's been a while since algebra. 

That's still a prime function however, so it's either a typo, or a trick question.
Report to moderator   Logged

Physics

  • ∇xE=-1/c·∂B/∂t, ∇·E=4πρ, ∇·B=0, ∇xB=1/c·∂E/∂t, F=q(E+v/cxB)
  • friend
  • Senior Member
  • ***
  • Posts: 1,315
Re: Sophomore Math Problem has me stumped
« Reply #7 on: January 07, 2011, 08:20:35 PM »
Quote from: JamisJockey on January 07, 2011, 07:27:20 PM
I taste purple.

Well, quit eating crayons then. =D
Report to moderator   Logged
In the world of science, there is physics.  Everything else is stamp collecting.  -Ernest Rutherford

RoadKingLarry

  • friends
  • Senior Member
  • ***
  • Posts: 21,841
Re: Sophomore Math Problem has me stumped
« Reply #8 on: January 07, 2011, 09:03:37 PM »
The answer is Bacon.
Report to moderator   Logged
If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or your arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that you were our countrymen.

Samuel Adams

AJ Dual

  • friends
  • Senior Member
  • ***
  • Posts: 16,162
  • Shoe Ballistics Inc.
Re: Sophomore Math Problem has me stumped
« Reply #9 on: January 07, 2011, 09:38:40 PM »
Report to moderator   Logged
I promise not to duck.

Phantom Warrior

  • friend
  • Senior Member
  • ***
  • Posts: 926
Re: Sophomore Math Problem has me stumped
« Reply #10 on: January 07, 2011, 11:04:55 PM »
Agree that the expression is not factorable.  4x^2+3x-7 is factorable to (4x+7)(x-1) but 4x^2-3x+7 is not factorable.  Confirmed with the Wolfram tool.
Report to moderator   Logged

Harold Tuttle

  • Professor Chromedome
  • friend
  • Senior Member
  • ***
  • Posts: 8,069
Re: Sophomore Math Problem has me stumped
« Reply #11 on: January 07, 2011, 11:27:35 PM »
it's a trick, get an axe
Report to moderator   Logged
"The true mad scientist does not make public appearances! He does not wear the "Hello, my name is.." badge!
He strikes from below like a viper or on high like a penny dropped from the tallest building around!
He only has one purpose--Do bad things to good people! Mit science! What good is science if no one gets hurt?!"

Nick1911

  • Administrator
  • Senior Member
  • *****
  • Posts: 8,492
Re: Sophomore Math Problem has me stumped
« Reply #12 on: January 07, 2011, 11:31:39 PM »
Report to moderator   Logged

Antibubba

  • friend
  • Senior Member
  • ***
  • Posts: 3,836
Re: Sophomore Math Problem has me stumped
« Reply #13 on: January 08, 2011, 02:26:52 PM »
42.
Report to moderator   Logged
If life gives you melons, you may be dyslexic.

Nightfall

  • friend
  • Senior Member
  • ***
  • Posts: 916
Re: Sophomore Math Problem has me stumped
« Reply #14 on: January 08, 2011, 06:27:53 PM »
I say not factorable as well. Maple 14 agrees with me.
Report to moderator   Logged
It is difficult if not impossible to reason a person out of a position they did not reason themselves into. - 230RN

Stetson

  • friends
  • Senior Member
  • ***
  • Posts: 1,094
Re: Sophomore Math Problem has me stumped
« Reply #15 on: January 08, 2011, 09:17:14 PM »
I checked it again and what I typed is correct.

She is going to put 'Equation is impossible to factor given the current paramenters'

If the teacher has a problem, the student has my number.
Report to moderator   Logged

AZRedhawk44

  • friends
  • Senior Member
  • ***
  • Posts: 13,990
Re: Sophomore Math Problem has me stumped
« Reply #16 on: January 08, 2011, 10:35:20 PM »
Is it bad that this same issue was presented on "Big Bang Theory?"

Leonard got an idea to build an iPhone app that can scan a handwritten polynomial or differential equation and interpret the characters, then factor it.

We are all geeks.  Long live the geeks. =D
Report to moderator   Logged
"But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."
--Lysander Spooner

I reject your authoritah!
Pages: [1]
« previous next »