Standard form of a Parabola

  • #1
Change the equation to standard form.

y = x^2 + 8x + 20


I thought this was the standard form for parabolas?? I tried this as the answer but it said it was wrong

y = (x+4)^2 +4

Thanks for the help! :-)
 

Answers and Replies

  • #2
symbolipoint
Homework Helper
Education Advisor
Gold Member
5,999
1,094
Complete the Square to the general form of the equation (and then undo this) and you will have something which is factorable. For your exercise, you want to add and subtract (8/2)^2 , and I will leave the rest of this for your effort to continue.
 
  • #3
okay so completing the square gives me

y = x^2 +8x + 20 + 16 - 16
y = (x^2 + 8x +16) + 4
then factor...

y = (x + 4)^2 + 4

which is exactly what I got before???
 
  • #4
symbolipoint
Homework Helper
Education Advisor
Gold Member
5,999
1,094
okay so completing the square gives me

y = x^2 +8x + 20 + 16 - 16
y = (x^2 + 8x +16) + 4
then factor...

y = (x + 4)^2 + 4

which is exactly what I got before???
That appears to be correct. That IS the standard form for your equation given in your exercise. The parabola has been shifted upward by 4 units and to the left by 4 units from standard position.
 
  • #5
okay thanks...I'll ask the teacher then, its an online submission homework so maybe somethings wrong. hopefully.
 

Related Threads on Standard form of a Parabola

Replies
3
Views
10K
  • Last Post
Replies
1
Views
5K
  • Last Post
Replies
2
Views
2K
Replies
2
Views
3K
Replies
3
Views
2K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
3
Views
9K
  • Last Post
Replies
5
Views
988
  • Last Post
Replies
7
Views
4K
Top