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    Hi guys, I have a retest tomorrow but Im stuck on some questions that I dont understand how I got them wrong.

    1) Simplify these fractions
    3x^/6x and 8x+16/2x-4
    For the first, I got 3x and for the second I got 4x+4, both of wich are marked wrong

    2) Make C the subject formular
    F=9/5 C+32
    I got C= 9/5 -32

    4) Solve the simultaneous equation
    2y-x=6
    y+x=4

    Thanks guys
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    1.
    - For the first one, note that \dfrac{3x^2}{6x} = \dfrac{3}{6} \times \dfrac{x^2}{x}; this isn't what you've got.
    - For the second one, I'm guessing the + on the top is meant to be a -? (Or vice versa?) Either way, take out common factors from the numerator and denominator, and remember that any number divided by itself is 1 (so for example \dfrac{x-3}{x-3} = 1 etc...)

    2.
    When you're making something the subject, you have to do a sort of reverse-BODMAS on it. For example, if y=2x+3 then first we subtract 3 from both sides, giving y-3 = 2x, and then we divide both sides by 2, giving \dfrac{y-3}{2} = x. You need to do a similar thing here.

    4.
    Notice that if you add the bottom equation to the top equation then then x terms will cancel and disappear, so do that. Alternatively, subtract 2 times the bottom equation from the top equation so that the y terms cancel and disappear.
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    (Original post by A1EX3)
    Hi guys, I have a retest tomorrow but Im stuck on some questions that I dont understand how I got them wrong.

    1) Simplify these fractions
    3x^/6x and 8x+16/2x-4
    For the first, I got 3x and for the second I got 4x+4, both of wich are marked wrong

    2) Make C the subject formular
    F=9/5 C+32
    I got C= 9/5 -32

    4) Solve the simultaneous equation
    2y-x=6
    y+x=4

    Thanks guys
    1) I can't tell what the first fraction is meant to be because the power is missing, but I suspect it's something to do with cancelling by 3. For the second fraction, the top can be factorised to incorporate the bottom, i.e.:

    \frac{(?x + ?)(2x-4)}{2x-4}

    I think you had the right idea but messed up one of the signs.

    2) To make C the subject, get that on its own on one side. Generally, rearrange the addition/subtraction first, then worry about the division/multiplication. In other words:

    F=9/5 C - 32

    F + 32 = 9/5C

    C = \frac{5(F+32)}{9}

    You can simplify that further if necessary.

    4) Number 3) seems to be missing. :p:

    To solve simultaneous equations, rearrange one equation to make a letter the subject (see 2)). Then, replace that letter with the expression on the other side of the equals sign in the other equation. You can solve this new equation to find a value of the variable, then put that value into the first two equations to get the other variable's value. This is solving simultaneous equations by substitution. If this method is too confusing, you can use the elimination method, but feel free to ask for clarification and I can walk you through it in more detail.

    Hope this helps.
 
 
 
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Updated: September 27, 2010
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