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iwanttogotostanford

  • one year ago

Please HELP: Using the completing-the-square method, rewrite f(x) = x^2 + 4x − 1 in vertex form. f(x) = (x + 2)^2 + 1 f(x) = (x + 2)^2 f(x) = (x + 2)^2 + 4 f(x) = (x + 2)^2 − 5

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  1. jdoe0001
    • one year ago
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    do you know what a "perfect square trinomial" is? sometimes just called a "perfect square"

  2. iwanttogotostanford
    • one year ago
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    yes

  3. zzr0ck3r
    • one year ago
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    \[x^2+bx+c=(x+\frac{b}{2})^2+c-\frac{b^2}{4}\]

  4. iwanttogotostanford
    • one year ago
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    would it be D then?

  5. Jhannybean
    • one year ago
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    \[f(x) = x^2+4x-1\]\[=(x^2+4x)-1\]\[=(x^2+4x+\color{red}{4})-1\color{red}{-4}\]\[=\boxed{(x-2)^2-5}\]

  6. jdoe0001
    • one year ago
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    so... \(\bf f(x)=x^2+4x-1\implies f(x)=(x^2+4x+{\color{red}{ \square ?}}^2)-1\) what do you think is the missing number?

  7. Jhannybean
    • one year ago
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    Lovely.

  8. zzr0ck3r
    • one year ago
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    correct @iwanttogotostanford

  9. iwanttogotostanford
    • one year ago
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    one more?

  10. Jhannybean
    • one year ago
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    @jdoe0001 why isn't `\boxed` working for me?

  11. iwanttogotostanford
    • one year ago
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    Which of the following values "completes the square," or creates a perfect square trinomial, for x2 + 6x + ___? 1 3 6 9

  12. iwanttogotostanford
    • one year ago
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    i believe its 9 but i just want to make sure

  13. Jhannybean
    • one year ago
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    \[c=\left(\frac{6}{2}\right)^2 = ~?\]

  14. iwanttogotostanford
    • one year ago
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    9!

  15. Jhannybean
    • one year ago
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    \[\color{red}{\checkmark}\]

  16. iwanttogotostanford
    • one year ago
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    i really need help with this one real quick, thanks for all your help..:-)

  17. iwanttogotostanford
    • one year ago
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    Solve x2 + 8x − 3 = 0 using the completing-the-square method. x = four plus or minus the square root of three x = negative four plus or minus the square root of three x = four plus or minus the square root of nineteen x = negative four plus or minus the square root of nineteen

  18. Jhannybean
    • one year ago
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    use the method we used above.

  19. iwanttogotostanford
    • one year ago
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    so , B?

  20. Jhannybean
    • one year ago
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    I don't know,I didn't solve it.

  21. iwanttogotostanford
    • one year ago
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    could you help me? :_)

  22. Jhannybean
    • one year ago
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    first add +3 to both sides.

  23. Jhannybean
    • one year ago
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    what do you get, @iwanttogotostanford ?

  24. iwanttogotostanford
    • one year ago
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    the same but on the left -6 and on the right 3

  25. Jhannybean
    • one year ago
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    ??....

  26. Jhannybean
    • one year ago
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    okay, if you add +3 to both sides , the answer i was looking for is, x\(^2\)+8x=3

  27. iwanttogotostanford
    • one year ago
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    @Jhannybean sorry, i was gone

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