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    phoenirius's Avatar
    phoenirius Posts: 34, Reputation: 1
    Junior Member
    		  
    #1

    Dec 15, 2005, 12:27 PM
    Solving for m and b
    How would you break down these equations to solve for m and b?

    9=-3m+b
    4=-m+b


    Thank you.
    Curlyben's Avatar
    Curlyben Posts: 18,514, Reputation: 1860
    BossMan
    		  
    #2

    Dec 15, 2005, 12:48 PM
    Quote Originally Posted by phoenirius
    How would you break down these equations to solve for m and b?

    9=-3m+b
    4=-m+b


    Thank you.
    OK I'll show you the first bit, its simple TAKING AWAY!
    9=-3m+b
    9+3m=b
    Now you can finish from here.
    CaptainForest's Avatar
    CaptainForest Posts: 3,645, Reputation: 393
    Ultra Member
    		  
    #3

    Dec 15, 2005, 01:00 PM
    -3m + b = 9, can be re-written b = 9 + 3m

    and, -m + b = 4

    Now sub for b, b = 9 + 3m:

    -m + b = 4

    becomes

    -m + (9 + 3m) = 4
    - m + 3m = 4 - 9
    2m = -5
    m = -2.5

    Now solve for b:
    -m + b = 4
    -(-2.5) + b = 4
    2.5 + b = 4
    b = 1.5

    Therefore, m = -2.5 AND b = 1.5
    phoenirius's Avatar
    phoenirius Posts: 34, Reputation: 1
    Junior Member
    		  
    #4

    Dec 15, 2005, 01:34 PM
    Now don't I feel silly!
    I was given answers in fractions and when I tried to solve it out I wasn't getting those answers, I thought I was wrong and way off. Thank you for helping me out and giving me a laugh at not seeing it sooner.
    s_cianci's Avatar
    s_cianci Posts: 5,472, Reputation: 760
    Uber Member
    		  
    #5

    Dec 18, 2005, 06:21 PM
    First, multiply one of them by -1 to make the b's cancel:

    -1(9=-3m+b) ---> -9 = 3m - b
    4=-m+b ---> 4 = -m + b

    Combine like terms and get: -5 = 2m
    Divide by 2 and get m = -5/2
    Plug this back in to one of the original equations and solve for b:

    4 = -(-5/2) + b
    4 = 5/2 + b
    4 - 5/2 = b
    3/2 = b
    fredg's Avatar
    fredg Posts: 4,926, Reputation: 674
    Ultra Member
    		  
    #6

    Dec 19, 2005, 06:57 AM
    Check your answers
    Hi, phoenirius,
    Do you know how to check your answers?
    Substitue the answers you get back into the first equation, see if it's true.
    Then, substitue the answer into the second equation, see if it's true.
    If both are true, then you have the correct answers.
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