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Math Help - algebraic expression

  1. #1
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    algebraic expression

    i have an algebraic expression to evaluate =

    8x+9y-(2x+y)

    x=4 and y =6

    this is how im doing it

    step 1 : 8x+9y -8x+ (-6y)
    answer book states answer is 72 how is that im suppose to get that number

    im severely confused as to what im doing wrong
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  2. #2
    Junior Member Mrdavid445's Avatar
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    Re: algebraic expression

    With the equation 8x+9y-(2x+y), we simply plug in 4 for x and 6 for y, thus giving us 8*4+9*6-(2*4+6)=72, our desired answer
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  3. #3
    Junior Member Mrdavid445's Avatar
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    Re: algebraic expression

    My question to you is why you turned -2x to -8x and -y to -6y?
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  4. #4
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    Re: algebraic expression

    We have not turned the -2x into -8x.We have put 4 in -2x=-2*4=-8
    -y=-6.
    so we get answer 72.
    trigonometry
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