## anonymous one year ago PLEASE HELP!!! f(x) = x^2 + 4x − 1 in vertex form

1. anonymous

@Nurali

2. butterflydreamer

hint: you want to use completing the square ^_^

3. anonymous

I don't know how to do that.

4. butterflydreamer

|dw:1439905794934:dw| So now you want to plug b = 4 into the formula: $(\frac{ b }{ 2})^{2}$ $= (\frac{ 4}{ 2 }) ^2 = 2^2 = 4$ Therefore to complete the square we have to add 4 $f(x) = x^2 + 4x - 1$ $= (x^2 + 4x + 4) - 1$ $= (x + 2)^2 -1$

5. butterflydreamer

oh oops. i made an error

6. butterflydreamer

Correction: f(x)=x2+4x−1 =(x2+4x+4)−1 - 4 We have to subtract 4 since we added 4 to complete the square =(x+2)^2−1-4 = (x + 2)^2 - 5

7. anonymous

lol nice, you pretty much got the concept down right though butterfly.

8. anonymous

thank you so much for explaining that for me :)

9. anonymous

can you help me with another question?

10. anonymous

Which of the following values "completes the square," or creates a perfect square trinomial, for x^2 + 6x + ___? a. 1 b.3 c. 6 d.9

11. butterflydreamer

use the formula i showed you above :) |dw:1439906543104:dw|

12. anonymous

9

13. butterflydreamer

excellent :)

14. anonymous

so the final result would be x^2 + 6x +9?

15. butterflydreamer

yyeess

16. anonymous

thank you so much! :)

17. butterflydreamer

no problemo~ ^_^