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Need help solving this quadratic equation using the zero-factor property?

Original Problem: 8/3 a^2 = 1 - 10/3a

The example from the book demonstrates on a problem like this x= 6/5 - 6/5x^2 and they show how you have to factor the 5 out and all that to get rid of the fractions. And then set the equation to 0 and then factor it out to find the 2 end answers of x. But my problem is when I go and try and do the same thing for the original problem, I am having trouble with that 1 after the equal sign and before the - 10/3 a. I'm not sure if I set that over too or what?

This is the work I have so far, which is likely incorrect, but I tried to follow the example as closely as I could:

3(a) = 3 (8/3a = possibly 1/3 - 10/3 a)

3(a) = 3 times 8/3a = 3 times 1/3 - 3 times 10/3

3a = 3 times 8a = 1/3 - 10a

After that I am rather confused and not even sure if I have the previous part of things going the right way. So any help on this would be great. Thanks.

5 Answers

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  • Eric W
    Lv 4
    1 decade ago
    Favorite Answer

    You're on the right track.

    8/3*a^2 = 1 - 10/3a

    You want to multiply both sides by 3. As long as you apply operations to both sides of the equation, you do not change the equation.

    3*(8/3*a^2) = 3*(1-10/3*a)

    8a^2 = 3 - 10a

    (don't forget that 3*8/3, the 3's cancel. You still ended up with 3 times 8a. Also remember that it is a^2 and not just a)

    Now you want to bring all the terms to one side and set it equal to zero

    8a^2 + 10a - 3 = 0

    And now you can factor. I'm assuming you know how to factor, but in case you do not I will point you to this tutorial:

    http://www.purplemath.com/modules/factquad.htm (in this case you'll want to factor the hard case)

    If you do factor you will find the answer is:

    (2a+3)(4a -1) = 0

    Now either 2a+3 = 0 or 4a-1 =0 since if either one of the terms is zero, and you multiply it by the other term, you still get zero.

    a = -3/2 or a = 1/4

    If you substitute this into the original equation you will find they do indeed equal zero. These are the roots of your equation.

    Hope this helps

    Cheers

  • j g
    Lv 5
    1 decade ago

    Multiply by three and get rid of the fractions:

    3[ 8/3 a^2 = 1 - 10/3a]

    8a²=3 - 10a

    Move the 10a and the 3 over.

    8a² + 10a - 3 = 0

    Now this is a quadratic equation that you can factor by guess and check or by grouping. I prefer factoring by grouping. To factor by grouping, multiply the coefficient of the squared term by the constant at the end, in this case, 8*-3 = -24. Are there factors of -24 that add to the middle 10? Yes, there are, +12, and -2.

    Rewrite the equation with these two numbers replacing the +10a.

    8a² + 12a - 2a - 3 = 0

    Factor the equation by grouping the first two terms and the last two terms.

    (8a² + 12a) +( - 2a - 3) = 0

    Factor the common factor from each:

    4a(2a + 3) -1(2a + 3) = 0

    Now refactor the common (2a + 3)

    (2a + 3)(4a - 1) = 0

    Solve each one:

    2a + 3 = 0

    2a = -3

    a = -3/2

    4a - 1 = 0

    4a = 1

    a =1/4

    These are your two answers.

  • 1 decade ago

    8/3 a² = 1 - 10/3 a

    24/3 a² = 3 - 30/10 a....(Multiply each term by 3, the LCD)

    8a² = 3 - 10a

    8a² + 10a - 3 = 0

    (2a + 3)(4a - 1) = 0

    If the product of two terms equals zero, then one or both terms equal zero.

    If 2a + 3 = 0,

    2a = - 3

    a = - 3/2

    If 4a - 1 = 0,

    4a = 1

    a =1/4

    a {- 3/2, 1/4}

    ¯¯¯¯¯¯¯¯¯¯¯¯

  • 1 decade ago

    1 = 3/3

    8/3 a^2 = 1 - 10/3 a

    8/3 a^2 = 3/3 - 10/3 a

    1/3 (8 a^2) = 1/3 (3 - 10 a)

    8a^2 = 3 - 10a

    8a^2 + 10a -3 = 0

    (4a -1)(2a+3) = 0

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  • ?
    Lv 4
    4 years ago

    that's very ordinary, only look on the equation and look at what 2 formula you multiply to get the unique. n^2 + 9n + 18 =0 ??? initiate by using using writing (n + _)(n + _) and look at what plus what = 9, and what situations what = 18. those 2 numbers could be waiting to do the two. racking your recommendations you get (n + 3)*(n + 6) = 0 to income that that's right, only do the multiplication returned: n^2 + 6n + 3n +18 = n^2 + 9n + 18. confident that's right! the zeros can now be examine off as n = -3, -6

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