division of polynomials

[nbalakers24]

y= 2x^3 - 3x^2 - 29x - 30

find x intercepts using the factor theorem.

i cant get the right solution :S

help appreciated!

[dodgedanpei]

If y=0, then x=-2
So then x+2 is a factor.

So divide 2x^3 - 3x^2 - 29x - 30 by x+2 by using long division.

[nbalakers24]

LOL thanks, that just made me realised my mistake i had (x-1) is a factor

[superflya]

ur linear factor will always be a factor of ur contant which in this case is ur k is 30 so the only possible factors are 1,2,3,5,10,15,30 and their neg values. The linear factor is usually single digits. Once u find the factor, take it's neg and use synthetic division, halfs ur working time.

[Stroodle]

ur linear factor will always be a factor of ur contant which in this case is ur k is 30 so the only possible factors are 1,2,3,5,10,15,30 and their neg values. The linear factor is usually single digits. Once u find the factor, take it's neg and use synthetic division, halfs ur working time.

Factors can also fractions.

[Ilovemathsmeth]

Factors can also be fractions, true. Also remember if one of your terms in the polynomial is missing, you need to add a coefficient of zero.

For example:

[superflya]

usually

[Ilovemathsmeth]

Same. I prefer long division.

[Stroodle]

I use both. Synthetic is good just because it's so fast...

Here's a good explanation on how to do it, if you're interested: http://www.purplemath.com/modules/synthdiv.htm

[superflya]

Synthetic division?? I'm only familiar with lonnnng division lol..

http://www.purplemath.com/modules/synthdiv.htm
http://www.purplemath.com/modules/synthdiv2.htm

more efficient and easier to check if u've made any simple calculation errors.

[the.watchman]

Long division is good, but seriously, shortcuts are handy!

Here's an example of what I use (when already known that it is a factor):

Say we're finding (i know it's easy, but for argument's sake...)

(the comes from and the comes from )

Expand the right-hand side:

From the above, we can see that

So, the quotient is

I think this is really easy when you practise it a few times, it all falls into place pretty quickly!

[brightsky]

Long division is good, but seriously, shortcuts are handy!

Here's an example of what I use (when already known that it is a factor):

Say we're finding (i know it's easy, but for argument's sake...)

(the comes from and the comes from )

Expand the right-hand side:

From the above, we can see that

So, the quotient is

I think this is really easy when you practise it a few times, it all falls into place pretty quickly!

That's cool.

[the.watchman]

Yeah it is, but it may take a while to get your head around it the first few times you try to use it!

[Stroodle]

That's the way our teacher taught us to do it too. She calls it the manipulation method. Saves so much time. I find synthetic division faster when has a large coefficient though.

[the.watchman]

That's the way our teacher taught us to do it too. She calls it the manipulation method. Saves so much time. I find synthetic division faster when has a large coefficient though.

Yeah, you're probably right...