If f(x)=2x^2-3x-(k+1)

Do I take c in the discriminant (b^2-4ac) as (k+1) or (-k-1)?

Surely I should take it as -k-1?

Thank you for your help

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- Sep 27th 2012, 01:10 PMMukilabSolving the discriminant
If f(x)=2x^2-3x-(k+1)

Do I take c in the discriminant (b^2-4ac) as (k+1) or (-k-1)?

Surely I should take it as -k-1?

Thank you for your help - Sep 27th 2012, 01:15 PMTheEmptySetRe: Solving the discriminant
- Sep 27th 2012, 01:32 PMMukilabRe: Solving the discriminant
So the answer would be k<17/8? (from 9-4(2)(-k-1) )

Thanks for the help! - Sep 27th 2012, 01:35 PMTheEmptySetRe: Solving the discriminant
- Sep 27th 2012, 01:39 PMMukilabRe: Solving the discriminant
Sorry! The question is:

The equation 2x^2-3x-(k+1)=0 where k is a constant, has no real roots. Find the set of possible values of k.

Therefore the discriminant must be <0 for f(x) to have no real roots. Therefore discriminant=(-3)^2-4(-k-1)(2)=17+8k

Therefore 17+8k<0

Therefore 8k<-17

Therefore k<-17/8 - Sep 27th 2012, 01:44 PMTheEmptySetRe: Solving the discriminant