Standard form of a Parabola

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! :-)
 

symbolipoint

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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.
 
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???
 

symbolipoint

Homework Helper
Education Advisor
Gold Member
5,276
803
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.
 
okay thanks...I'll ask the teacher then, its an online submission homework so maybe somethings wrong. hopefully.
 

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