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kevin8374

  • 2 years ago

solve for r r^2+3r=8 Example r^2+3r=1 r=-3+√13/2,-3-√13/2

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  1. philips13
    • 2 years ago
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    looks like the quadratic equation might help here

  2. brinethery
    • 2 years ago
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    r^2 +3r -8 =0 a=1 b=3 c=-8 Use the quadratic formula to get your answer(s) for x.

  3. kevin8374
    • 2 years ago
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    The quadratic equation is where my problem lies

  4. brinethery
    • 2 years ago
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    Do you know what the quadratic formula is?

  5. brinethery
    • 2 years ago
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    http://0.tqn.com/d/create/1/0/i/9/9/-/Quadratic.formula.jpg

  6. brinethery
    • 2 years ago
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    ((-1) +/- sqrt ((3)^2-(4)(1)(-8)))/((2)(1))

  7. brinethery
    • 2 years ago
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    (-1 +/- sqrt (41))/2 ***THAT MEANS*** x = (-1 + sqrt(41))/2 x = (-1 - sqrt(41))/2

  8. kevin8374
    • 2 years ago
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    Thanks so much

  9. brinethery
    • 2 years ago
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    This is what you do whenever factoring is impossible.

  10. brinethery
    • 2 years ago
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    Or if you're too lazy to factor :-)... like I usually am LOL

  11. kevin8374
    • 2 years ago
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    so how would i put x^2+7x=10 into the quadratic equation

  12. brinethery
    • 2 years ago
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    Okay so your format is going to be ax^2+bx+c So with x^2+7x=10, you always always always get everything on the left side. You're setting it equal to zero. x^2+7x-10=0 Now what are a, b, and c?

  13. kevin8374
    • 2 years ago
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    sorry typed problem wrong x^2+7x-10=0

  14. brinethery
    • 2 years ago
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    k... so what do you think a, b, and c are?

  15. kevin8374
    • 2 years ago
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    a is 1 b is 7 c is 10

  16. brinethery
    • 2 years ago
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    Yup!

  17. brinethery
    • 2 years ago
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    I'll ask you one now. -x^2+2x+3 What is "a" in this case?

  18. kevin8374
    • 2 years ago
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    -1

  19. brinethery
    • 2 years ago
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    yep

  20. kevin8374
    • 2 years ago
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    my problem is keeping it all in order

  21. brinethery
    • 2 years ago
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    Now if there's a term, say b=-2 and you need to plug it into your formula, the first thing you're putting in is -b. So how to do that: -(-2). So that will be a +2.

  22. brinethery
    • 2 years ago
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    I understand. And I would recommend to do the problem in as many steps as you need to. And to slow down and pay close attention. I took an engineering problems course last quarter and I made a lot of mistakes when I didn't pay attention :-)

  23. brinethery
    • 2 years ago
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    You can try that problem and we'll compare answers if you want.

  24. kevin8374
    • 2 years ago
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    ok is it -7+√89/2,-7-√89/2

  25. brinethery
    • 2 years ago
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    That's what I got too. You know what you're doing!

  26. kevin8374
    • 2 years ago
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    You have no idea how much you have helped me thanks again!!!!!

  27. brinethery
    • 2 years ago
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    I'm glad :-) So step 1: Get everything on the left side so that it's set equal to zero. step 2: write down what your a, b, and c values are step 3: plug in to the formula and go slow

  28. kevin8374
    • 2 years ago
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    I truly cannot thank you enough I have been struggling for days

  29. brinethery
    • 2 years ago
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    I would recommend Paul's online notes as an alternative to your book. Most algebra books truly suck. http://tutorial.math.lamar.edu/Classes/Alg/SolveQuadraticEqnsII.aspx

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