factorize y=-2x^2+8x+4

[GheeTsar]

My guess is b) =1

The reason being is that there could be an infinite number of 9s after the decimal place meaning that it is essentially 1?

I'd pick B too. But then I got a C at maths A-level and can't remember much about what I did learn then!

[LWA]

No, it's never 1. It's always <1.

It's convienient to think of it as equivalent to 1 sometimes, and you rely on that sometimes, as with approximations as it's approaching 1.

Doesn't it depend on whether we are talking about real numbers? (this is really stretching my maths...)

Wikipedia (and yes I know!) states the following:

In mathematics, the repeating decimal 0.999… which may also be written as 0.\bar{9} , 0.\dot{9} or 0.(9)\,\! denotes a real number equal to one. In other words, the notations 0.999… and 1 represent the same real number. This equality has long been accepted by professional mathematicians and taught in textbooks. Proofs have been formulated with varying degrees of mathematical rigour, taking into account preferred development of the real numbers, background assumptions, historical context, and target audience.

Let x = 0.9 (rec)

10x = 9.9 (rec)

10x - x = 9.9 (rec) - 0.9 (rec) = 9

9x = 9

x = 1

=> 0.9 (rec) = 1

QED.

Edit: interesting reading.....

https://nrich.maths.org/discus/messa...613/68880.html
https://nrich.maths.org/discus/messa...613/67006.html

[KalC]

heh, nerds!

just joking, good luck with your question mate

[irth1ing]

Doesn't it depend on whether we are talking about real numbers? (this is really stretching my maths...)

Wikipedia (and yes I know!) states the following:




Let x = 0.9 (rec)

10x = 9.9 (rec)

10x - x = 9.9 (rec) - 0.9 (rec) = 9

9x = 9

x = 1

=> 0.9 (rec) = 1

QED.

Edit: interesting reading.....

https://nrich.maths.org/discus/messa...613/68880.html
https://nrich.maths.org/discus/messa...613/67006.html

nice findings..
but b is right..

given in the example in the sites, :

1/9=0.11111111
3/9=0.33333333
6/9=.666666666
therefore 9/9=0.99999999

also 9/9 also =1..

this is just part of the fun i picked up in my juniors, which something i cannot forget trying to disproof.. lol... those were happy days...

[Dareos]

I asked Jeeves



he didnt know either

[Zak33]

I'd like to think that with a degree in electrical engineering, I'd be able to solve that.

So, I'm not going to try. Ignorance is bliss.

Looks like everyone else has it covered though. Keep up the good work, everyone!

I'd like to think that with an O level in Maths (grade A, done with mild hangovers) and a total Ungraded in Maths A level (how on earth were those two levels of exam SOOOO far apart) I'd like to think I have totally forgotten how to factoris/ze, with an S or a Z.

But I can cheer you on towards finding the result

[Lucio]

I'd like to think I knew the answer, but I don't, because it's been ages since I last studied or used maths beyond the basic stuff.

[TheAnimus]

I asked Jeeves



he didnt know either

Ask Wolfram Alpha
http://www.wolframalpha.com/input/?i=-2x^2%2B8x%2B4

(edit forum crapping up the link. paste "-2x^2+8x+4" into search box)

he knows.

[mycarsavw]

But what are these questions for?

See the "The "Post-count and other rewards" thread" link in Funkstar's sig

[bsodmike]

The purpose of factorisation is to simply isolate the roots of the characteristic equation, i.e. (x+2)(x+2) = 0 essentially means double roots at x = -2

The only solution as I see it is x = -0.45 (to 2 d.p.) and x = 4.45; I simply used the formula x = [-b±(b^2-4ac)^0.5]/2a

I remember a simple rule to find if a quadratic equation can be easily factorised. If the result of
(b^2-4ac)^0.5 is a perfect square it'll work out; else you have to use the equation.

edit: I tried TheAnimus's suggestion, it works quite nicely!

http://www.wolframalpha.com/input/?i=-2x^2%2B8x%2B4

x = 2 - (6)^0.5 and x = 2 + (6)^0.5 which is the same result as the decimal values I gave above.

[irth1ing]

I asked Jeeves



he didnt know either

lmfao!!!

[irth1ing]

Ask Wolfram Alpha
http://www.wolframalpha.com/input/?i=-2x^2%2B8x%2B4

(edit forum crapping up the link. paste "-2x^2+8x+4" into search box)

he knows.

nice link.. cheers!! now she can use this for her homework..

[pipTheGeek]

I got an A at GCSE, a C at A Level and an E at A level further maths...

and I can't remember how to complete the square
I do remember learning it though. I also recently realised that I can't remember how Differentiation or integration any more. I really hope one of my kids does A level maths.

[TheAnimus]

nice link.. cheers!! now she can use this for her homework..

Do make sure she understands the principle of it thou! Otherwise she could find herself stuck in exams.

[irth1ing]

Do make sure she understands the principle of it thou! Otherwise she could find herself stuck in exams.

lol

she's really not that bright, but there's alots of examples to give her an idea how.. i think..

seems there's alot of good websites for maths.. i'm so glad...