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eli123

  • 2 years ago

factor 21x^2-49x-9x-21

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  1. eli123
    • 2 years ago
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    idk how i got 7x(3x-7) 3(3x-7) and i know its wrong

  2. hartnn
    • 2 years ago
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    is the original problem 21x^2-58x-21 ?

  3. eli123
    • 2 years ago
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    no

  4. eli123
    • 2 years ago
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  5. hartnn
    • 2 years ago
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    right,so thats 21x^2-40x-21=0 right ?

  6. eli123
    • 2 years ago
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    yeah and then the product of 21 and -21 is -441 and then 40 so the two numbers are -49 and 9

  7. hartnn
    • 2 years ago
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    that is correct, see above u have written -49x - 9x instead of what u got now as -49x+9x

  8. eli123
    • 2 years ago
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    oooh i see wow

  9. hartnn
    • 2 years ago
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    now whats common from first 2 terms in 21x^2-49x-9x-21 =0?

  10. eli123
    • 2 years ago
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    7x

  11. eli123
    • 2 years ago
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    i got the answer :P -3/7 and 7/3

  12. hartnn
    • 2 years ago
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    yup, correct.

  13. eli123
    • 2 years ago
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    im having problems with another equation

  14. hartnn
    • 2 years ago
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    which ?

  15. eli123
    • 2 years ago
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  16. eli123
    • 2 years ago
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    i got to the point 9 + or - sqrt of 1 all over 4

  17. hartnn
    • 2 years ago
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    9 from where ?

  18. hartnn
    • 2 years ago
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    Compare your quadratic equation with \(ax^2+bx+c=0\) find a,b,c then the two rots of x are: \(\huge{x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}}\)

  19. eli123
    • 2 years ago
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    yeah b is 9

  20. hartnn
    • 2 years ago
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    nopes, b is -4

  21. eli123
    • 2 years ago
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    oh wait nooo i gave you the wrong equation! no wonder

  22. hartnn
    • 2 years ago
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    lol :P

  23. eli123
    • 2 years ago
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  24. hartnn
    • 2 years ago
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    still b is -9

  25. eli123
    • 2 years ago
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    but in that equation it says -b so -(-9) is 9

  26. eli123
    • 2 years ago
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    inside i did put put -9^2 = 81

  27. hartnn
    • 2 years ago
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    yes, u are correct \(\huge\frac{9 \pm \sqrt{1}}{4}=\frac{10}{4},\frac{8}{4}\)

  28. eli123
    • 2 years ago
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    wait you are just adding and subtracting the 1?

  29. eli123
    • 2 years ago
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    obviously lol never mind i feel stupid

  30. hartnn
    • 2 years ago
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    got it now ?

  31. eli123
    • 2 years ago
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    yes, it was a stupid moment :P

  32. eli123
    • 2 years ago
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    ok i did another one and i got 4+-sqrt of 28 all over 2 @hartnn

  33. hartnn
    • 2 years ago
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    question ?

  34. eli123
    • 2 years ago
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    its the first one that sent you

  35. eli123
    • 2 years ago
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  36. hartnn
    • 2 years ago
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    thats correct :)

  37. eli123
    • 2 years ago
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    but how do i factor it?

  38. hartnn
    • 2 years ago
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    do u want to factor or do u want to use quadratic formula? anyways its not factorable....

  39. eli123
    • 2 years ago
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    so what would be the answer?

  40. eli123
    • 2 years ago
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    i cant simplify it?

  41. hartnn
    • 2 years ago
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    all u can do is \(2 \pm \sqrt7\)

  42. hartnn
    • 2 years ago
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    \(\sqrt{28}=2\sqrt7\)

  43. eli123
    • 2 years ago
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    how does that equal to that

  44. hartnn
    • 2 years ago
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    \(\sqrt{28}=\sqrt{7*4}=\sqrt{7}\sqrt{4}=2\sqrt{7}\)

  45. eli123
    • 2 years ago
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    got it

  46. eli123
    • 2 years ago
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    you are the best!

  47. hartnn
    • 2 years ago
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    lol. glad to hear that :) u too are awesome ;)

  48. eli123
    • 2 years ago
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    lol thank you, well i gotta keep doing this stupid hw

  49. hartnn
    • 2 years ago
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    best of luck for that.

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