anyone good at maths.

[jodahunter]

Just been doin me maths homework and my minds gone blank about real roots and ****.. anyway if u could help it would be great. Question:

X squared + 6x + m = 0 has no real roots for x

find the set of values that m can take.



Now i know that no real roots means that the "X squared + 6x + m < 0", but i'm still stuck :(

drivin me crazy cos i know it really should be piss easy, i just cant do it.

[Tim]

Gah, I'm doin the a level so I should be able to do this

36- 4m < 0 so 36 < 4m 9<m

I think, it's the taken from the bit inside the square root of the quatdratic formula.

[Pie In The Sky]

I havn't got any paper by me and I am not going to attempt to work it out.
However that is a quadratic equation, so use the formula to work it out, which is
x= [-b +/- square root of (b squared - 4ac) ] over 2a
Then you can re-arange. If you can't get that then I will work it out when I can be bothered to go get some paper and pen :cool:

[Tim]

I havn't got any paper by me and I am not going to attempt to work it out.
However that is a quadratic equation, so use the formula to work it out, which is
x= [-b +/- square root of (b squared - 4ac) ] over 2a
Then you can re-arange. If you can't get that then I will work it out when I can be bothered to go get some paper and pen :cool:

yeah that's what I thought. It's been ages since I did this sort of stuff. If there's no roots what's inside the square root can't be done so it has to be less than 0.

[jodahunter]

ahhh, so b squared - 4ac < 0.

Nice one lids.

[Pie In The Sky]

Wait a minute I think I'm getting it.
Using the formula I put above. If a=1 b=6 and c=?
the that means it is -6 +/- square root 36-4*1*? all over 2
then you can use trial and error to work out m if x=0.
I think :S
I don't know that's as far as I got.

[jodahunter]

it works out that

6 squared - 4 x 1 x m < 0

36 - 4m <0

36 < 4m

9 < m

or m > 9

[Tim]

Wait a minute I think I'm getting it.
Using the formula I put above. If a=1 b=6 and c=?
the that means it is -6 +/- square root 36-4*1*? all over 2
then you can use trial and error to work out m if x=0.
I think :S
I don't know that's as far as I got.

You don't need the rest of the equation for what he's trying to do because the equation has no roots. X=/= anything. My first post shows what M is without using trial and error.

[KninjA]

Uhhh is that the full question?

[Tim]

it works out that

6 squared - 4 x 1 x m < 0

36 - 4m <0

36 < 4m

9 < m

or m > 9

yup that's it.

[jodahunter]

thats all there was.

[Pie In The Sky]

Pffft oh well I tried.
I'm only GCSE standard anyways :o