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Quadratic formula problem.

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Benjo
Posts: 709 - Karma: 23
i got a problem in maths so please help me

2x + 3         4x+7
--------  +   -------   = 7
2x-3           2x-4



another one:


x(x-5) -3 = (2x-1)² -4


please show me the whole way
Apr 21 2010 10:40AM
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Milksteak
Posts: 9948 - Karma: 833
Someone should have payed attention in class..
Apr 21 2010 10:42AM
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.frenchy
Posts: 18221 - Karma: 12,321
for the second one are you solving for x, or am i stupid lol?
Apr 21 2010 10:44AM
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beowulf
Posts: 893 - Karma: 164
what else would you solve for...
Apr 21 2010 10:49AM
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dubaiski
Posts: 961 - Karma: 37
as far as i can see you dont need he quadratic formula for either

the second one is 0=(x+1)(x-1) so X= 1 or -1

the first is long winded and i cant be bothered.

i did it quickly so check it over before you hand it in
Apr 21 2010 10:55AM
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comeatmebro
Posts: 10720 - Karma: 66
for the 2nd i believe you get x=0 and x=-1/3. so x=-1/3. don't wanna type out the work really.
Apr 21 2010 10:57AM
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Benjo
Posts: 709 - Karma: 23
i'll check it

+k for sure anyway
Apr 21 2010 11:08AM
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Benjo
Posts: 709 - Karma: 23
+k also for you sir
Apr 21 2010 11:09AM
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dubaiski
Posts: 961 - Karma: 37
scrap that, the guy above me was right, i forgo to carry an x. And BTW it snot hard, i wont write it all out because you wont learn from it. Just square out the brackets, move it all to one side and factorise.

pm me if you have any questions
Apr 21 2010 11:12AM
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chacho
Posts: 183 - Karma: 33
heres how i got -1/3 for x, its pretty easy

x(x-5)-3=(2x-1)^2-4
2x-5x-3=(2x-1)(2x-1)-4
-3x-3=4x-2x-2x-2
-3x-3=0-2
-3x=1
-x=1/3
x=-1/3

Apr 21 2010 11:28AM
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Benjo
Posts: 709 - Karma: 23
thank you
+k
Apr 21 2010 11:43AM
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SOLID7
Posts: 239 - Karma: 11
Quadratic formulas often have two answers so be careful -_-. Try solving this one for fun:

Square root of -6. It's easy, trust me.
Apr 21 2010 12:32PM
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chapz
Posts: 10182 - Karma: 66
2x + 3 4x+7
-------- + ------- = 7
2x-3 2x-4


ok well i think you can just use cross multiplication...

2x+3/2x-3 = 4x+7+14x-28/2x-4
(2x+3)(2x-4) = (2x-3)(18x-21) ->(i cross multiplied, after using common denominator of 2x-4 on right hand side)
(4x^2 -2x-12) = (36x^2 -42x-54x+63)
(4x^2 -2x-12) = (36x^2 -96x+63)
4x^2 -2x-12-36x^2+96x-63=0
-32x^2 +94x-75=0 -> solve using quadratic formula

might not work, but it should.
Apr 21 2010 12:37PM
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lahnabonny
Posts: 1260 - Karma: 35
x times x = x squared, not 2x
Apr 21 2010 12:44PM
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J.DUKE
Posts: 1233 - Karma: 38
yes. i knew something looked funny
Apr 21 2010 1:24PM
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reazzysteezy
Posts: 3 - Karma: 10
no you can't cross multiply until you solve the left side for one fraction. you can cross multiply when you have a fraction = a fraction
Apr 21 2010 1:36PM
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Bepo
Posts: 8195 - Karma: 17
I never knew ns was so mathematically challenged
Apr 21 2010 1:43PM
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BootySpunk.
Posts: 8148 - Karma: 84
I will give you hints.

1. Find a common denominator and than set the equation equal to 0 by subtracting 7.

2. Don't be an idiot and do some simple ass foiling and algebra and set the equation equal to zero by doing algebraic stuff.
Apr 21 2010 2:20PM
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Steezy_IN_KC
Posts: 2033 - Karma: 1,607
This might help you a little bit now.. and probably down the road a bit...


works for me.
Apr 21 2010 2:35PM
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no_steeze
Posts: 23992 - Karma: 4,272
i literally learned this in 7th grade
Apr 21 2010 2:43PM
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Benjo
Posts: 709 - Karma: 23
thanks to all of you guys! kinda helped me out...

btw its pretty funny to discuss about maths. lol
Apr 21 2010 3:01PM
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samsquamch
Posts: 342 - Karma: 96

2nd problem is x=0, x=-1/3 get those answers by completing the square and gettin one side equal to  0 (so that you can derive x using the quadratic formula). the -4ac will cancel because there is no c value in your equation you'll plug in, so dont worry about your equation looking funny

the first one i dont really feel like doin but get a common denominator and bring the 7 to the other side if you want to use the quadratic formula to solve for x because one side has to be equal to zero for the quadratic formula to work

Apr 21 2010 3:54PM
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karmagod
Posts: 925 - Karma: 11
Seriously, how fucking old or stupid are you? You're dealing with super basic algebra problems there. You should seriously learn this shit rather than ask NS to do your homework for you.
Apr 21 2010 4:59PM
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killa_cam
Posts: 13143 - Karma: 15
1) Multiply both sides by (2x-3)*(2x-4). x=1.625=13/8, x=4.5=9/2

2) Just expand. x=0, x=-0.33=-1/3
Apr 21 2010 5:26PM
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mathmansam
Posts: 293 - Karma: 40
anything is a fraction if you put it over 1....
Apr 21 2010 5:32PM
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chapz
Posts: 10182 - Karma: 66
i did...
did you not look over my work?
Apr 21 2010 6:44PM
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