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Math Help - [SOLVED] substitution

  1. #1
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    [SOLVED] substitution

    if y=as+b/x and if y= 13 when x = 1 and y = 20 when x=2, find the values of a and b and the value of s for which y is a minimum.

    I have tried substitution but i can't seem to get hte right answer maybe i'm doing it wrong
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by chibiusagi View Post
    if y=as+b/x and if y= 13 when x = 1 and y = 20 when x=2, find the values of a and b and the value of s for which y is a minimum.

    I have tried substitution but i can't seem to get hte right answer maybe i'm doing it wrong
    do you mean y = \frac {as + b}x or y = as + \frac bx ?

    anyway, use the first two things given to set up simulataneous equations to solve for a and b

    then take the derivative of the function (with a and b plugged in) and set it equal to zero and solve for s. you can check that this is a minimum using the second derivative
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