trigonomentry help!!!

if one of the root of the equation ax^2+bx+c=0 is four times the other show that 4b^2-25ac=0...
help please show working plz

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asked by Philip
  1. (x-q)(x-4q) = a x^2 + b x + c

    x^2 - 5qx + 4 q^2 =a x^2 + bx + c
    if a = 1
    b = -5 q
    c = 4 q^2

    then
    4 b^2 = 100 q^2
    and
    25 a c = 100 q^2
    and
    100 q^2 -100 q^2 = 0 all right

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    posted by Damon

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