SOLUTION: it is given that the axis of symmetry of the graph of the function y=x^2+kx+5 is x＝-3. Find the value of k.

Algebra ->  Functions -> SOLUTION: it is given that the axis of symmetry of the graph of the function y=x^2+kx+5 is x＝-3. Find the value of k.      Log On


   

Question 1005918: it is given that the axis of symmetry of the graph of the function y=x^2+kx+5 is x＝-3. Find the value of k.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!

Complete the square to get to vertex form,
y=x%5E2%2Bkx%2B%28k%2F2%29%5E2%2B5-%28k%2F2%29%5E2
y=%28x%2Bk%2F2%29%5E2%2B5-%28k%2F2%29%5E2
The vertex lies on the axis of symmetry so when x=-3,
-3%2Bk%2F2=0
k%2F2=3
k=6