#1
I need some help with some precalculus thing.....

f(x) = x^2 -2x

find the values for which f(x) > 15
find the range of f.
#3
46?? uh, its a bit of work, but could you type out the steps?? Im a bit of a dunce
#4
x ≥ 5

I think... I failed pre cal and did this in my head.

EDIT:
Quote by Confuse-a-Cat
f(x) will be greater than 15 for any value of x greater than 5.


You can call me Aaron.


♠♣♥♦
Out on parole, any more instances of plum text and I get put back in...
Last edited by biga29 at Dec 6, 2011,
#6
The answer is 200. Which also happens to be the wattage of the amp you need.
Quote by Zaphod_Beeblebr
Theory is descriptive, not prescriptive.


Quote by MiKe Hendryckz
theory states 1+1=2 sometimes in music 1+1=3.
#7
Quote by biga29
x ≥ 5

I think, I failed pre cal and did this in my head...



It's only >5, can't equal


TS is shit at math ...
#8
Quote by Zeletros
It's only >5, can't equal


TS is shit at math ...


Oh, ok. Because the question was for everything greater than 15, not greater than or equal to 15 right?
You can call me Aaron.


♠♣♥♦
Out on parole, any more instances of plum text and I get put back in...
#9
Quote by biga29
Oh, ok. Because the question was for everything greater than 15, not greater than or equal to 15 right?



Yes, and also TS is shit at math
#10
Quote by Zeletros
It's only >5, can't equal


TS is shit at math ...



I know!
#13
Quote by OsmanAli
ok, find the coefficient of x^4 in the expansion of (2-x^2)(1-2x^2)^8



Ok, find the coefficient of x^4 in the expansion of (2-x^2)(1-2x^2)^8, yourself
#14
Quote by OsmanAli
ok, find the coefficient of x^4 in the expansion of (2-x^2)(1-2x^2)^8
This isn't what your mom meant when she said to do your homework.

Also, there is a huge math thread with a bunch nerds who get boners for stuff like this.
You can call me Aaron.


♠♣♥♦
Out on parole, any more instances of plum text and I get put back in...
#15
My atttempt at a... I'm a but rusty in the language of Mathematics.

x² – 2x > 15
x² – 2x – 15 > 0
(x – 5)(x + 3) > 0


(x - 5) <- - -(-3)- - -(5)----->
(x + 3) <- - -(-3)-----(5)----->
f(x) .. <-----(-3)- - -(5)----->

- - - Negative
----- Postive



Therefore,
f(x) > 15 when:
x < (-3) or x > 5

When x is either grater than 5 or less than negative 3.
ERROR 0x45: Signature not found
Last edited by sfaune92 at Dec 6, 2011,
#16
^ And now I feel rather silly for forgetting that there would also be a negative answer. That's what I get for looking at it and thinking '5' rather than working it through properly...

Quote by OsmanAli
ok, find the coefficient of x^4 in the expansion of (2-x^2)(1-2x^2)^8


We're not here to just give you all of your answers.

Expand the brackets. It's simple, although with that power of 8 it might take a couple of minutes. You'll get your coefficient of x^4.
#17
Expanding the brackets is a really long way of doing the question. Use the binomial expansion to find the coefficients in the second term that, when multiplied by either the 2 or the -x^2 will give x^4.
#20
Quote by DarthPeanuts
Expanding the brackets is a really long way of doing the question. Use the binomial expansion to find the coefficients in the second term that, when multiplied by either the 2 or the -x^2 will give x^4.


Ah yes, good point. It's been so long since I've done one of those, I think I'd forgotten it existed.
#22
Cheat and use wolframalpha....or you know, learn to do it yourself.
The content of this signature is pretty much irrelevant