A few days ago
brownfriend19

Factoring a Quadratic, I need help…?

Factor the polynomial and use the factored form to find the zeros. then sketch the graph…(this is what I am suppose to do, but I am having difficulty factoring this equation.)

p(x)= 2x^3-x^2-18x+9

I tried factoring by factoring a 2 out then you end up with 9/2 in the equation…which I cannot figure how to factor into binomals to find my zero…also tried dividing the whole thing by 2 but its just the same thing…any help would be great, also formula if you used one, and instruction would be really helpful! thank you in advance!

Top 4 Answers
A few days ago
please.blowme

Favorite Answer

This is not a quadratic its a cubic lol.

P(3)=2(3)^3-(3)^2-18(3)+9

=0

therefore one factor (x-3)

now divide the original function by that factor, then you get

2x^2+5x-3

factorise the above again then you get:

(2x-1)(x+3)

and so the whole function factorised is

(x-3)(2x-1)(x+3)

to find zeros just equate all of them to zero and find x

eg (x-3)=0

X=3

to graph the polynomial find all the x intercepts again equate all the factors to zero (x-3)(2x-1)(x+3) and find x.

then sub x=0 to find y intercept.

you could also differentiate the original funtion to find the turning points and get a very accurate graph.

This sounds really complicated but its quite simple. it draws from several previously learnt(that you should have learnt =p) concepts and combines them. if you have any problems ask again!

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4 years ago
Anonymous
one million). x^2 – 7x + 6 = 0 (x – one million) (x + 6) = 0 x = one million and x = 6 2). 3x^2 + x – 2 = 0 (3x – 2) (x + one million) = 0 x = 2/3 and x = -one million 3). x^2 – 9x – 36 = 0 (x – 12) (x + 3) = 0 x = 12 and x = -3 4). 3x^2 + 7x – 6 = 0 (3x – 2) (x + 3) = 0 x = 2/3 and x = -3 ok….
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A few days ago
Maverick
There is no short quick way to do these…..in fact, you have to do it somewhat like long division…..they are NASTY!!!!

sorry to have to tell you that.

Suggest you look at the following site for help….

http://mathworld.wolfram.com/SyntheticDivision.html

I cannot explain it any better than they can!

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A few days ago
omicron_gray
Do u know synthetic division?Try doing that.

Answer would be:(2x-1)(x+3)(x-3)

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