# Quadratic discriminant with tricky algebra

sooyong94

## The Attempt at a Solution

I did b^2 -4ac>=0, but the algebra becomes prohibitively difficult.

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Dearly Missed

## The Attempt at a Solution

I did b^2 -4ac>=0, but the algebra becomes prohibitively difficult.

Sometimes there are just no shortcuts, and lengthy algebra cannot be avoided. That being said, I am not sure the result sought is correct; in particular, in your second equation you have a constant ##d## appearing in it, but there is no ##d## in the first equation.

sooyong94
I got something like
ab-4ac-ad+bc+bd-cd but I can't seem to work around that.

Irene Kaminkowa
In the second equation there is a misprint
The correct equation is
(a+c-b)x2-2(a-c)x+(a+c+b) = 0
The proof is not difficult. Just find the discriminant.

Homework Helper
Dearly Missed
I got something like
ab-4ac-ad+bc+bd-cd but I can't seem to work around that.

What about the issue I raised? There is a ##d## in the second equation, but no ##d## in the first one. The relation between ##a,b,c## arising from the first equation does not involve any ##d## at all.

sooyong94
In the second equation there is a misprint
The correct equation is
(a+c-b)x2-2(a-c)x+(a+c+b) = 0
The proof is not difficult. Just find the discriminant.
Thanks - I guess there's a misprint in my book after all.

sooyong94
Strangely enough I got -b^2 -4ac, which isn't right.

Update - I found an algebraic slip in my working.

sooyong94
I have managed to work the first part - but I don't have a clue on tackle the second part.

Update - I managed to work this out.

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