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/sci/ - Science & Math

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5529819 No.5529819[DELETED]  [Reply] [Original]

I'm in an algbra 2 class, and I missed about half of a unit on polynomials. I hate polynomials. How would I go about simplifying
(x+3)(x-2)(x+7)
(Don't give me the answer however)
I will also post a few other questions throughout the duration of this thread.
>Also general questions thread

>> No.5529833

shameful bump

>> No.5529836

>>5529819
((x+3)(x-2))*(x+7)
(x^2-2x+3x-6)(x+7)
7x^2-14x+21x-42 + x^3-2x^2+3x^2-6x
x^3+8x^2+x-42

also wolfram alpha

>> No.5529843
File: 11 KB, 200x202, pa.6.036.png [View same] [iqdb] [saucenao] [google]
5529843

>>5529819
1. Underage b&
2. Foil the first two, then use the box method for what you get. Alternatively, you can just foil what you have left.
F(irst) O(uter), I(nner) L(ast) - FOIL (Basically just distribute)
(x+3)(x-2) = I no gibe yuu dee answer = Let's call this y
(x+7)(y)

>> No.5529844

>>5529836
Thanks dude, I'm good now so I'mma let this thread die.

>> No.5529845

>>5529836
just finished algebra 2
>http://www.youtube.com/watch?v=FxTiogyhwfc
this will tell you how

>> No.5529858

>>5529845
>working according to these systems
i seriously hope you dont accustom this

>> No.5529884
File: 6 KB, 469x252, 5124123123.png [View same] [iqdb] [saucenao] [google]
5529884

>>5529819

What's this foil shit that you plebs are talking about...

If you have to use mnemonics in maths, you should go kill yourself.

Pic related: that's how shit should be looked at and solved.

>> No.5529905

>>5529884
>doesn't know the FOIL method

pffffhahahaha

>> No.5529911

>>5529905
shhhh, don't worry, his Alegbra teach didn't know how to teach math.

Twas horrible; he was likely the only one that passed.

>> No.5529928

>>5529884
please stop being edgy you are scaring the children

>> No.5529936
File: 252 KB, 300x100, 45.gif [View same] [iqdb] [saucenao] [google]
5529936

>>5529884
>If you have to use mnemonics in maths, you should go kill yourself

it must suck to have your ego

>> No.5529958

OP back with more
How do i solve trinomials with missing terms.
Ex:
X to the 4 - 3x to the 2 +2
And im having issues solving
X^5+5x^2+12x+10

>> No.5529960

>>5529884
I see absolutely no measurable way memorizing your stupid little picture isn't as prole as the mnemonic.

>> No.5529969

>>5529936
my favorite banner of all fucking time

4chan in a 300X100 picture

>> No.5529982

>>5529960
>>5529969
Is sci really this cancerous?
Srs guiz
Srsly

>> No.5530020
File: 9 KB, 459x377, 000000000000000100.png [View same] [iqdb] [saucenao] [google]
5530020

>>5529958

Google:
Rational Roots Theorem.

x^4 - 3x^2 +2
But, in this case, you can make a substitution.
x^4 - 3x^2 +2
w = x^2.
(x^2)^2 - 3(x^2) + 2

w^2 - 3w + 2 = 0
Solve with the quadratic formula.
Then when you end up with your 2 w's, sub that back into (w=x^2) to get the 4 x solutions.

There should be at least 1 real solution per degree of the highest polynomial (In this case:4)

>> No.5530037

>>5530020
There must be a way to solve that first one with factoring

>> No.5530040

>>5529958

You will definitely need the rational root theorem for this..

x^5+5x^2+12x+10

Did your teacher/lecturer leave you a hint in the question.. eg. "x=1 is a solution"

Anyway, when x=b is a solution, (x-b) is a factor. similar to the brackets in the OP.

>> No.5530053

>>5530037

Factoring will do fuck all..

x^4 - 3x^2 +2
x^2(x^2 - 3) +2

Substitution is how you solve these.

>> No.5530056

>>5530040
Holy shit im getting it

>> No.5530078

OP... Are you in Grade 8 or 9?

>> No.5530084

>>5530078
Well. For the sake of the rules I'm an 18 year old senior in alg2 next year I'll be NINEteen
But I try to stay within the top ten of my class
math to say the least, is not my strength lately

>> No.5530086

>>5530084
Although I used to be good, like in my foreign language courses, but winging some chapters has given me a poor base

>> No.5530091

Another question:
Last one i think
How do i calculate the multiplicity

>> No.5530088

>>5530084
this is ninth grade math, you're lying

>> No.5530093

>>5530088
Of course I am

>> No.5530098

>>5530091

It's the number of times the curve touches the x-axis and where.

Draw a graph to help; or use wolfram.

>> No.5530102

>>5530020
What and where do i get the "w"

>> No.5530124

>>5530102

It's just the letter I used for the substitution.

You can put a triangle in there for all anyone cares, it's just there to say:

Let w = x^2.

Now, remember out power rules.

((a^n)^m) = a^(nm)

Well, think of
x^4 as ((x^2)^2) = x^(2*2)

Because, w=x^2

We then get ((x^2)^2) = ((w)^2) or just w^2

It reduces the 4th order to a quadratic, which is easily solvable; just don't fuck up and forget to substitute the 2 'w' values back into 4 'x' values.

Eg. Solutions for w = a, b
w=x^2
x= sqrt(a), -sqrt(a), sqrt(b), -sqrt(b)

>> No.5530132

>>5530124
I love you sir. If this weren't a sfw board you would have testosterone increasing images.

>> No.5530136

>>5530093
i hope you get a 5 year ban

>> No.5530159

>>5530136
But really, I'm turning 19 in a bit

>> No.5530209

>>5529958
If you have an equation like AX^2+BX+C=0 (wich is this case i think) you need to find 2 numbers: lets say, N and M. N+M=B. N*M=AC.

So, in this equation, you need to find 2 numbers that added are -3 and multiplied are 2. Those numbers are -2 and -1. Then you replace.

So

<span class="math">x^4-2x^2-x^2+2=x^2(x^2-2)-1(x^2-2)=(x^2-1)(x^2-2)[/spoiler]

And because that multiplication equals 0, x^2 must be 1 or 2.