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    carchemishk's Avatar
    carchemishk Posts: 1, Reputation: 1
    New Member
     
    #1

    Jun 24, 2009, 07:38 AM
    solve 3 questions
    25x^2+80x+64


    15z^2+14z-8

    write the expression in lowest term
    2x+2
    ______
    6x^2+16x+10
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
    Uber Member
     
    #2

    Jun 24, 2009, 08:00 AM

    You need to know how to factorise, according to the numbers given.

    1.
    See +64 and +80x? That shows that you have to find positive factors of 64, which are +1, +2, +4, +8, +32 and +64.



    By trial and error, you'll have;



    using the +8 factors of +64, and the factors of 25.

    2.Could you try that out now?

    3. Factorise the denominator and the numerator, you'll see that something's will cancel out, giving a simpler fraction.
    Perito's Avatar
    Perito Posts: 3,139, Reputation: 150
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    #3

    Jun 24, 2009, 08:06 AM





    write the expression in lowest term
    This appears to be about factoring. Let's take the first one.



    1. Note that 25 and 64 are both perfect squares. 25 = 5*5; 64 = 8*8. 8 and 5 are, therefore, prime candidates for coefficients in the factored terms.

    2, All terms are positive. Therefore, it will factor into something like this:

    where a and c aren't necessarily different. In fact, since you've got a perfect square, a and c may be equal and b and d may be equal.

    ... And, I see that Uknown008 posted the answer. Make sure you understand what he did.

    Let's look at the second problem.



    1. 15 and 8 aren't perfect squares so we can't hope for anything simple like in #1. 15=3*5; 8=2*2*2. Since 15 has only two factors, we can expect 3 and/or 5 to be a coefficient (but only because problems are usually crafted this way). Also, 2 and 4 (2*2) are likely candidates for coefficients.

    Since the signs of the terms are +, +, - we would expect to factor using this form:



    of course because must be greater than ad because the second term is positive.

    Now let's look at #3.



    You can factor a 2 out of the numerator and the denominator. That would probably be a good idea right off the bat, so as to simplify things a tiny bit.



    The 2 will divide out. Now it appears that we have an (x+1) in the numerator. Since the denominator is a quadratic expression, we should probably factor it to see if an (x+1) term appears that we can cancel out. Because the coefficients are all positive, we will again expect to factor the denominator into the form: and, in fact, we'll expect (if the problem was written the way most problems were written),

    Give it a whirl.

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