Write the given function in vertex form by completing the square:
y=x^2+9x+2

Question

Write the given function in vertex form by completing the square: 
y=x^2+9x+2

myininaya · Answer

Ok! So 
$$x^2+9x+k$$
How do you find k so that this is a complete square?

myininaya · Answer

$$x^2+9x+(\frac{9}{2})^2=(x+\frac{9}{2})^2$$
This will always work if the coefficient of x^2 is 1
Just divide the number in front of x by 2 then square like I did above

myininaya · Answer

Now back to finding the vertex form!

myininaya · Answer

$$y=x^2+9x+(\frac{9}{2})^2-(\frac{9}{2})^2+2$$
Whatever I add in I must also take out

myininaya · Answer

The form we are aiming for by the way is:
$$y=a(x-h)^2+k$$

myininaya · Answer

So You should be able to write that one part (x^2+9x+(9/2))^2) as a complete square which I at the beginning of this thread

myininaya · Answer

And then all you have to do after simplify if you can such as the -(9/2)^2+2 part

anonymous · Answer

thankyou!