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Math Help - Algebra Question

  1. #1
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    Algebra Question

    1-Find all numbers that, Rational Expression is not defined;
    (Hint, Factor Denominator))
    _2X 10__
    X2 - 8X + 15

    formCheckList.addElement(new Check_Answer({ref_label:"2",name:"mc-ans-_8413333_1"}));
    a.
    The Numbers are: X = - 5 and X = - 3

    b.
    The Numbers are: X = 5 and X = 3

    c.
    The Numbers are: X = 5 and X = - 3

    d.
    The Numbers are: X = - 5 and X = 3
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by rdfisch View Post
    1-Find all numbers that, Rational Expression is not defined;
    (Hint, Factor Denominator))
    _2X – 10__
    X2 - 8X + 15

    formCheckList.addElement(new Check_Answer({ref_label:"2",name:"mc-ans-_8413333_1"}));
    a.
    The Numbers are: X = - 5 and X = - 3

    b.
    The Numbers are: X = 5 and X = 3

    c.
    The Numbers are: X = 5 and X = - 3

    d.
    The Numbers are: X = - 5 and X = 3
    Hello rdfisch,

    Before we get started on this question. It doesn't belong in The Advanced algebra section.(alot of folks wont look here). Try using Algebra or urgent help for a faster responce.

    Since we are not allowed to divide by zero, we want to find all values of x that would make the denominator zero.

    x^2-8x+15=0 since the b term (the middle one) is negative and the c term (the constant) is positive both factors must be negative.

    so we need factors of 15 that add up to -8

    the factors of 15 are 1,15 and 3,5

    since 3+5=8 this is what we want so we get...

    x^2-8x+15=0 \iff (x-3)(x-5)=0

    setting each factor equal to zero and solving we get x=3 and x=5

    I hope this helps.
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  3. #3
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    Joined
    Apr 2008
    Posts
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    answer

    The answer is where x=5 and x=3, so b.

    because x^2 - 8x + 15 = (x-5)(x-3)

    Any numbers that make the denominator 0 makes the expression not defined.




    Quote Originally Posted by rdfisch View Post
    1-Find all numbers that, Rational Expression is not defined;
    (Hint, Factor Denominator))
    _2X 10__
    X2 - 8X + 15

    formCheckList.addElement(new Check_Answer({ref_label:"2",name:"mc-ans-_8413333_1"}));
    a.
    The Numbers are: X = - 5 and X = - 3

    b.
    The Numbers are: X = 5 and X = 3

    c.
    The Numbers are: X = 5 and X = - 3

    d.
    The Numbers are: X = - 5 and X = 3
    Follow Math Help Forum on Facebook and Google+

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