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anonymous

  • 5 years ago

Solve for x, X^2+6x-40=0

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  1. anonymous
    • 5 years ago
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    You can either factor or use the quadratic formula.

  2. anonymous
    • 5 years ago
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    I am not quite sure how to do that.

  3. anonymous
    • 5 years ago
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    This one is factorable, so lets do that.

  4. anonymous
    • 5 years ago
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    Because it is an x^2 with no number multiplied by it, we know it will be in the form (x+?)(x+?)

  5. anonymous
    • 5 years ago
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    Have you done FOIL yet?

  6. anonymous
    • 5 years ago
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    No I have no idea what that is

  7. anonymous
    • 5 years ago
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    If we have something like this (x-4)(x+3) you can expand it by using a method called FOIL.

  8. anonymous
    • 5 years ago
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    First Outside Inside Last

  9. anonymous
    • 5 years ago
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    you multiply the terms like that and add them together

  10. anonymous
    • 5 years ago
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    in this example, we would end up with x^2 +3x -4x -12

  11. anonymous
    • 5 years ago
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    which simplifies to x^2 -x -12

  12. anonymous
    • 5 years ago
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    Now, notice that that looks a whole lot like the problem you started with! We are going to do FOIL backwards.

  13. anonymous
    • 5 years ago
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    X^2+6x-40 we are looking for two numbers that when multiplied give us -40, but when added give us 6.

  14. anonymous
    • 5 years ago
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    they can be positive or negative, and they'll be integers in a basic problem such as this. Any numbers come to mind?

  15. anonymous
    • 5 years ago
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    How about 4 and -10?

  16. anonymous
    • 5 years ago
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    So, we end up with this: (x+4)(x-10) When FOILed, we get this: X^2+6x-40 Remember, this is set equal to zero so we have ended up with (x+4)(x-10)=0

  17. anonymous
    • 5 years ago
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    Now we can solve it. This equals zero when x is either -4 or 10.

  18. anonymous
    • 5 years ago
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    This is how I got that: you can set both parts equal to zero: x-4=0 x+10=0 solving, we get x to equal -4 and 10.

  19. anonymous
    • 5 years ago
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    oops, i meant this: This is how I got that: you can set both parts equal to zero: x+4=0 x-10=0 solving, we get x to equal -4 and 10. Quadratic equations like these have two answers the majority of the time, so the answer would be x=-4, 10

  20. anonymous
    • 5 years ago
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    err, scratch that

  21. anonymous
    • 5 years ago
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    Back when I first said "How about 4 and -10?" I got the signs backwards. So x actually comes out to equal 4 and -10 in the end... sorry

  22. anonymous
    • 5 years ago
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    Did you get all that? Kinda confusing the first time around...

  23. anonymous
    • 5 years ago
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    It's fine. Thank you for your help! I really appreciate it. I kind of understand. Im pretty bad at math.

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