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    I got to part (b) and now I'm stuck. I have a+b = 7 and -8a+4b = 4 and now I don't know how to go about getting the value of a and b
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    (Original post by jessnoch)
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    I got to part (b) and now I'm stuck. I have a+b = 7 and -8a+4b = 4 and now I don't know how to go about getting the value of a and b
    You have two equations. Two unknown values. How do you reduce it to one unknown value?
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    (Original post by High Stakes)
    You have two equations. Two unknown values. How do you reduce it to one unknown value?
    I don't know, I think I'm being dumb
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    (Original post by jessnoch)
    I don't know, I think I'm being dumb
    If a + b = 7, then a = 7 - b right?

    How can I use that information in the other equation?
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    To get the value of a and b, you have to solve the two equations simultaneously.

    The two equations we have are:

    a + b = 7 and -8a + 4b = 4.

    Rearrange the first equation to make a the subject.
    a = 7 - b

    Subsitute the rearranged equation into the second equation of -8a + 4b =4.

    -8(7 - b) + 4b = 4

    Simplify This subsitution to solve for b by expanding the brackets:

    -8(7 - b) + 4b = 4 = -56 + 8b + 4b = 4

    Now solve for b( collecting like terms)
    (move the -56 to the other side to get +56 so that makes 12b = 60
    12b = 60
    b = 5

    Subsituteb = 5into any of the equations to find the value of a:

    a = 7 - (5)
    a = 2

    So you values for a and b are:

    a = 2 and b = 5.
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    (Original post by crystala1998)
    ...
    Please don't post full solutions - it's against the rules of this forum.

    The first half of your post would have been great to allow the OP to finish it themselves.
 
 
 
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