more help on quadratics (1 Viewer)

[ta1g]

In the quadratic equation -3x^2 - (k+1)x + 5=0 , the roots are equal in magnitude but opposite in sign. Find the value of k.

 

[kami]

root 1 = alpha
root 2 = -alpha
-b/a = -(-(k+1))/-3 = (k+1)/-3 = alpha + (-alpha) = 0
:. (k+1) = 0
:. k= -1

 

[Riviet]

This is a little more concise:
Let the roots be p and -p
sum of roots = p-p
=0
.: -b/a = 0
(k+1)/-3 = 0
k = -1

 

[acmilan]

Thats exactly the same thing kami did.

 

[Riviet]

Woops, lol