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Math Help - Rearrange to find X.

  1. #1
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    Rearrange to find X.

    How do I rearrange this to find X?
    X(A + 2B) = 10
    I don't really get what I have to do to rearrange it.
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  2. #2
    Super Member craig's Avatar
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    Quote Originally Posted by Aihem View Post
    How do I rearrange this to find X?
    X(A + 2B) = 10
    I don't really get what I have to do to rearrange it.
    This is not as hard as it looks. You have factorised the left hand side and taken out a common factor of X.

    Have you tried dividing both sides by (A + 2B), see what happens
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  3. #3
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    I don't really understand what you mean. I thought rearranging was doing the reverse of what is input in a function machine. So
    3X + 3 = 6 would be X --> [*3] --> [+3] = 6 reversed to be 6 -> [-3] -> [/3] = X = 1. I'm confused with brackets. Would the answer be
    X = 10 ?
    (A + 2B)
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  4. #4
    Super Member craig's Avatar
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    Quote Originally Posted by Aihem View Post
    I don't really understand what you mean. I thought rearranging was doing the reverse of what is input in a function machine. So
    3X + 3 = 6 would be X --> [*3] --> [+3] = 6 reversed to be 6 -> [-3] -> [/3] = X = 1. I'm confused with brackets. Would the answer be
    X = 10 ?
    (A + 2B)
    Yes that is pretty much it.

    If it is easier, try to think of "(A + 2B)" as just a number, lets say 2. If our expression was 2X on the left hand side, then you would have no problem dividing by 2 to get an expression for X.

    The same rule applies for "(A + 2B)", as X is multiplied by the whole of this bracket, then we can just divide both sides by (A + 2B), you are then left with:

    X = \frac{10}{A + 2B}

    Hope this clears it up a bit
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  5. #5
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    So
    X(3A + B) = Z would be X = Z/ (3A + B)

    I'm stuck on this one now  <u>20    </u> = 5
    X * X
    Ps. How do I get the Squared symbol?
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  6. #6
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    Quote Originally Posted by Aihem View Post
    So
    X(3A + B) = Z would be X = Z/ (3A + B)
    Yes. In "AX= Z", because X is multiplied by A, you do the opposite: divide both sides by A to get X= Z/A. It doesn't matter how complicated "A" is: in X(3A+ B)= Z X is multiplied by 3A+B so you multiply both sides by it.

    I'm stuck on this one now  <u>20    </u> = 5
    X * X
    Ps. How do I get the Squared symbol?
    Was this supposed to be 20= \frac{5}{x^2}?

    If so, first multiply both sides by x^2, to get 20x^2= 5, then divide both sides by 20 to get x^2= \frac{5}{20}k. Finally, since x is squared on the left, "undo" that by taking the square root of both sides. That will be much easier if you reduce the fraction \frac{5}{20}!
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  7. #7
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    What do you mean by taking the square root of both sides? How would I do that to 5/20?
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  8. #8
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    5/20 = 1/4. Square root of 1/4 is simply 1/2.
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