The discriminant is equal to the first derivative.
Does that have any special meaning (geometrically or otherwise), or is it just an algebraic coincidence?
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4tran2007-07-01 22:27 ID:JRUBkP0j
That's not even true...
The first derivative is a function from C->C
The discriminant is a number in C
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Anonymous2007-07-02 8:44 ID:uYNyxYVp
Don't discriminate against numbers >_<
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Anonymous2007-07-02 11:34 ID:owvDG3dp
You should ask this guy I know; he's an expert programmer cause he's read SICP.
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Anonymous2007-07-03 17:09 ID:rUQcepFA
AX^2 + BX + C = 0
(+/-)sqrt(B^2 - 4AC) = 2AX + B
manipulates into the quadratic formula
The reason I was asking is because I read it in some vedic math books. Most of the stuff in there becomes common sense after a bit of thinking, but this just seems like it's out there.
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Anonymous2007-07-03 18:49 ID:mdDjn8Mq
(+/-)sqrt(B^2 - 4AC) = 2AX + B
in the above, X is the value which makes the quadratic function zero, whereas in the first derivative, x is a function of y.
also, the discriminant is the expression under the root sign,
d=b^2-4ac
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Anonymous2007-07-03 18:51 ID:mdDjn8Mq
>>6
oops y is a function of x, in other words, x can vary.
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4tran2007-07-04 1:33 ID:nvRkiG81
mmm, I see what you're saying. It's probably better phrased as "the discriminant is equal to the derivative at the roots".
What I do know: if the discriminant is 0, then there exists a real, double root. This also requires the derivative to be 0 at the root. In this case, they are equal. This should generalize to higher order polynomials.
What I'm speculating: when the discriminant is not 0, this is probably just an algebraic coincidence.
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Ikerous2007-07-04 3:53 ID:QU8jHCKW
the quadratic formula is -b/2a (+/-) sqrt(b^2 - 4ac)/ 2a = x
-b/2a is the vertex of the parabola. The sqrt(b^2 - 4ac) is the distance on each side (Hence +/-) from the vertex to the zero's.
The vertex of a parabola exists when the first derivative is zero. 2ax + b = 0 when X = -b/2a. Hence the relationship.