Question

Factorize 2x^3 - 7x^2 - 39x + 60
Pls provide detailed answer with pen and paper working..........

Answer 1

Hey Amistre !!!

Can u help with this !!!!

Answer 2

http://en.wikipedia.org/wiki/Cubic_equation

Answer 3

thanks estudier !!!

But the boy has not been taught these advanced methods. For quadratic polynomials only cases which can be solved by factorisation have been taught.

For cubic polynomials, they hv been taught to find a factor by hit-and-trial method. then u divide the cubic polynomial by this factor to get a quadratic polynomial which u split to get the two remaining factors.....

I can't apply that method to this question.....

Can Amistre help with this ??????

Answer 4

If rational roots/guess and check plus usual calculus methods are all ruled out, then there is nothing to be done.

Even if those methods were allowed it is a lot of calculations for 3 non integer roots.

Answer 5

2x^3 - 7x^2 - 39x + 60 ; if its gonna be easy, then the rational roots will find it

Answer 6

2x^3 - 7x^2 - 39x + 60

1,2,4,3,6,12,5,10,20,15,30,60
---------------------------
1,2

thats alot of trials and errors to sort thru :)

Answer 7

a) Not allowed
b) It has 3 nasty roots.

Answer 8

might be easiest with synthiec division to check results

Answer 9

oww!! my eyes!!! .... nasty indeed

Answer 10

since the roots arent well behaved; this way is simply not going to work

Answer 11

Trouble is, H is ruling out everything useful, derivatives, sign changes, rational roots, etc.

Even with them, it's very difficult.

About the only way is the depressed cubic which is something a computer should bedoing.

Answer 12

you sure you aint got a typo?

we could approximate it with numerical analysises

Answer 13

Also not allowed.

Answer 14

my version of numerical analysis is akin to trial and error :)

Answer 15

guess and check..

Answer 16

yep, when it changes sign, back up and add smaller

Answer 17

or subtract smaller til it changes again

Answer 18

Ok, so what's your first guess (pretend you're a boy....)?

Answer 19

I posted it becoz when I went through it myself I cud see that it was not solvable by the method that the student had been taught.......

Just to be 100% sure before I told him to talk to his teacher about an "out of course" question, I thought I should consult you guys......

Now that I am sure, we can ask the teacher to award marks for this question to all students....

Answer 20

my first guess would be a good round number, not to much filler, and a hint of cinnamon: 10

Answer 21

Isn't 1 easier?

Answer 22

2000 - 700 - 390 + 60 .... 1 might be easier, but im a boy lol

Answer 23

:_)

Answer 24

10 results in a positive number so lets back it up to 5..

Answer 25

When do these so called "summer schools" end?

Answer 26

around 28 if your lucky

Answer 27

Is it like "remedial"?

Answer 28

Or is it extra?

Answer 29

summer school serves to purposes here in the states; retake a class to get a passing score; take a class so that you dont have to take it during normal school sessions

Answer 30

Ah, I see...

Answer 31

I was going to say, I don't know how much more summer school I can take, lol.

Answer 32

5 pops out a negative number so someplace between 5 and 10 is a zero; lets go to 7

7 is positive; try 6. 6 is positive; try 5.5 etc ..

Answer 33

yeah, the quality of questions lately seems to have deteriorated :)

Answer 34

We have to get 1.34 3.77, 5.93 approx...

Answer 35

So ur headed for the last...

Answer 36

Let's say u get it...

Answer 37

yep, its the only way id be able to get "close" to any roots ;)

Answer 38

Then you go play ninrendo, right..?

Answer 39

nintendo

Answer 40

super mario brother indeed

Answer 41

Right, let's go see what's been posted,,,,