another quadratic question (1 Viewer)

[RideTheLightnin]

hey guys

"Find p if the quadractic px^2 + 2x +7 = 0 has roots that are reciprocals"

ok so you make the roots a and 1/a, but then im not sure what to do after. This is what i get

a + 1/a = -b/a
a + 1/a = 2/p

and a.1/a=c/a
a.1/a=7/p

not sure what happens next....
cheers

 

[VivianHsu]

"Find p if the quadractic px^2 + 2x +7 = 0 has roots that are reciprocals"

let roots be A and 1\A
product of roots: A*1\A=1=7\p
.: p=7

 

[Riviet]

I don't think you can do the question since the product of the roots 1/a and a is always equal to 1 and the 7 means this can never happen. Therefore there are no values of p that satisfy the condition.

 

[VivianHsu]

I don't think you can do the question since the product of the roots 1/a and a is always equal to 1 and the 7 means this can never happen. Therefore there are no values of p that satisfy the condition.

product of roots
=A*1\A
=1
=7\p

when p=7, 7/p = 1
so p=7 satisfies the condition