PDA

View Full Version : (x+3)(x-5)(x-2)?

lymepink
05-26-2011, 10:45 PM
The question says write a polynomial in standard form using the following zeros: -3,5,2.
I got it down to the step of (x+3)(x-5)(x-2) but i dont know how to multiply those together.. fast help would be wonderful. Darn final tomorrow.

tkhunny
05-27-2011, 12:40 AM
It is just multiplication. Why are you struggling with this? Surely you have multiplied binomials before. No?

lymepink
05-27-2011, 08:59 AM
If I knew how to do it, I wouldn't have posted it.

Denis
05-27-2011, 02:53 PM
Your math teacher gave this out without teaching how?

tkhunny
05-27-2011, 03:27 PM
If I knew how to do it, I wouldn't have posted it.

You have this quite backwards. It's the stuff you cannot post that is what you don't know.

So, you're actually saying you cannot expand this multiplication of binomials (x + 1) * (x + 2) into its equivalent trinomial?

Please try. Really, it's just multiplication - just like 23 * 47.

mmm4444bot
05-27-2011, 07:20 PM

FOIL is an acronym for "First-Outside-Inside-Last". These are four steps that comprise an algorithm for multiplying two binomials.

There are lots of examples and lessons. Come back here and post any specific questions that arise.

Here is FOIL symbolically:

(a + b)*(c + d) = a*c + a*d + b*c + b*d

lymepink
05-27-2011, 07:40 PM
I know how to foil a set, it just slipped my mind how to multiply these three together. So far no one has even posted the answer...
but it's fine now because I figured it out this morning, I was just hoping someone would post a fast answer last night while I was doing my review sheet. I don't know how this site works exactly. Thanks for the suggestions.

And tkhunny or whatever your name is, your last comment didn't even make sense. Stop trying to get smart on a math website people use for help. I obviously forgot how to do the problem, I don't need someone telling me how I dont know how to do a problem. It would have been much appreciated for help, not for your irrelevant comments.

tkhunny
05-29-2011, 02:31 AM
What did you do to solve it? Was it something other than multiplication?

wjm11
05-29-2011, 02:33 AM
The question says write a polynomial in standard form using the following zeros: -3,5,2.
I got it down to the step of (x+3)(x-5)(x-2)

The multiplication is simple. Start by multiplying any two of the factors -- for example, the first two: x^2 - 2x - 15. Now just multiply each of these three terms by the remaining two terms.

lookagain
05-29-2011, 02:27 PM
I know how to foil a set, it just slipped my mind how to multiply these three together.

lymepink,

also the multiplication can be done in a vertical style:

- \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \longrightspace \ \ \ \ \ \ \ x^2 \ \ - \ 2x \ \ - \ 15
- \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \longrightspace \longrightspace \longrightspace \ \ \ \ \ x \ \ - \ \ \ 2
.- \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ---------
- \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ -2x^2 \ \ + \ \ \ 4x \ + \ 30
- \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x^3 \ \ - \ 2x^2 \ \ - \ 15x
.- \ \ \ \ \ \ \ \ \ \ \ \ \ -- - - - - - - - - - - -
- \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x^3 \ \ \ - \ 4x^2 \ - \ \ 11x \ + \ 30

Also, see this for vertical style examples:

http://www.purplemath.com/modules/polymult.htm

Denis
05-29-2011, 03:12 PM
LymePink, I'm kind of a positional freak (like, I throw with my left hand, do everything else with my right hand!);
with these, I'm only comfortable if I go left to right this way:

x^2 - 2x - 15
x - 2
================
x^3 - 2x^2 - 15x
- 2x^2 + 4x + 30
=====================
x^3 - 4x^2 - 11x + 30

Try it, perhaps you'll like it :idea:

mmm4444bot
06-05-2011, 04:43 PM
So far no one has even posted the answer ...

I was just hoping someone would post a fast answer last night

That's not how it works, at this site.

I don't know how this site works exactly.