SOLUTION: hi can somebody please help me with this question? for what value(s) of k will the function g(x)=x^2+kx+1 have only one zero A.0 B.2 C.-2,2 D. no values will work. Thank you

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: hi can somebody please help me with this question? for what value(s) of k will the function g(x)=x^2+kx+1 have only one zero A.0 B.2 C.-2,2 D. no values will work. Thank you       Log On


   



Question 1090501: hi can somebody please help me with this question?
for what value(s) of k will the function g(x)=x^2+kx+1 have only one zero
A.0
B.2
C.-2,2
D. no values will work.
Thank you so much.

Found 2 solutions by Fombitz, greenestamps:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
The quadratic needs to be a perfect square.
%28x%2Ba%29%5E2=x%5E2%2B2a%2Ba%5E2
So a%5E2=1
a%5E2-1=0
%28a%2B1%29%28a-1%29=0
a=-1
a=1
So then,
k=2a
k=-2 and k=2

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!

In the quadratic formula, the discriminant, b^2-4ac, tells you whether the quadratic expression has two, one, or no real zeros. If the discriminant is positive, there are two zeros; if it is 0, there is one zero (a double root); if it is negative, there are no real zeros.

So in your example, there is only one zero if the discriminant is zero:
b%5E2-4ac+=+k%5E2-4%281%29%281%29+=+k%5E2-4+=+0
k%5E2-4+=+0
%28k%2B2%29%28k-2%29+=+0

The values -2 and 2 each make the discriminant equal to 0.

So answer C, -2 and 2.