Hi all..

I've a question which requires to me to find a positive and negative real root for values of p...the equation is...

x^2 +px +8=p

Find the values of p has one positive and one negative root.

Many thanks!

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- Jul 14th 2010, 07:27 AMsilvercooHelp with finding a positive and negative root
Hi all..

I've a question which requires to me to find a positive and negative real root for values of p...the equation is...

x^2 +px +8=p

Find the values of p has one positive and one negative root.

Many thanks! - Jul 14th 2010, 07:47 AMearboth
- Jul 14th 2010, 07:50 AMsilvercoo
Hi!

Many thanks for your help..

just wondering, why cant I use b^2 - 4ac >0 ? - Jul 14th 2010, 08:05 AMearboth
- Jul 14th 2010, 08:07 AMsilvercoo
Correct, then i would need to equate it to >0

so i should obtain (p+8)(p-4)>0

which would lead to

p<-8 or p>4...

Edit

Pardon me, it should be p>= 4

Edit, again

Nope...its still <-8 or p>4...

sorry about this.. - Jul 14th 2010, 08:24 AMearboth
- Jul 14th 2010, 08:29 AMearboth
- Jul 14th 2010, 08:47 AMsilvercoo
Hey thanks. I think i managed to figure it out already..

thanks once again! =) - Jul 14th 2010, 08:53 AMrunning-gag
The product of the roots of the quadratic equation ax˛+bx+c=0 is c/a

Therefore to get a positive and a negative root for you must have a negative product : 8-p < 0 or p > 8