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    The gradient of the line perpendicular to 2y=cx-3 is -2. Find C?
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    (Original post by Chelsea12345)
    The gradient of the line perpendicular to 2y=cx-3 is -2. Find C?
    Yeah, so if the gradient perp to this line is -2, then the gradient of this line must be 1/2. Get this line in the form of y=mx+c then do m=1/2 and solve for c.
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    (Original post by Chelsea12345)
    The gradient of the line perpendicular to 2y=cx-3 is -2. Find C?
    1. Rewrite in the form y=mx+c
    2. Use the fact that if two perp. lines have gradients m_1,m_2 then m_1 m_2=-1
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    Rearrange equation into the form y=mx+c, input your gradient into the equation (it will not be -2, rather the reciprocal) and then you should get a value for c.
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    (Original post by RDKGames)
    Yeah, so if the gradient perp to this line is -2, then the gradient of this line must be 1/2. Get this line in the form of y=mx+c then do m=1/2 and solve for c.
    i got the first bit but how do i solve for C? do i put the gradient back into the equation or something?
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    (Original post by Chelsea12345)
    i got the first bit but how do i solve for C? do i put the gradient back into the equation or something?
    You create a linear equation with C being the only unknown and you solve for it. No substitution needed.
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    (Original post by RDKGames)
    You create a linear equation with C being the only unknown and you solve for it. No substitution needed.
    Thankyou!
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    (Original post by natsciguy)
    A line perpendicular to a line always has a negative reciprocal gradient.

    If the gradient of the line is -2, then the negative reciprocal is -1/-2 or 1/2.

    To get the equation in standard form (y=mx+c) we must divide through by 2 to get y=c/2x-1.

    As c/2 is the gradient (as it is the coefficient of x) then 1/2=c/2. Therefore c=1.
    Full solutions are not allowed
 
 
 
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