- #1

sooyong94

- 173

- 2

## Homework Statement

## Homework Equations

Quadratic discriminant

## The Attempt at a Solution

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

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- Thread starter sooyong94
- Start date

- #1

sooyong94

- 173

- 2

Quadratic discriminant

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

- #2

Ray Vickson

Science Advisor

Homework Helper

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## Homework Statement

## Homework Equations

Quadratic discriminant

## 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.

- #3

sooyong94

- 173

- 2

I got something like

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

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

- #4

Irene Kaminkowa

- 66

- 14

The correct equation is

(a+c-b)x

The proof is not difficult. Just find the discriminant.

- #5

Ray Vickson

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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.

- #6

sooyong94

- 173

- 2

Thanks - I guess there's a misprint in my book after all.

The correct equation is

(a+c-b)x^{2}-2(a-c)x+(a+c+b) = 0

The proof is not difficult. Just find the discriminant.

- #7

sooyong94

- 173

- 2

Update - I found an algebraic slip in my working.

- #8

sooyong94

- 173

- 2

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.

Update - I managed to work this out.

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