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## apple_pi 2 years ago Roots of quadratic:

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1. apple_pi

if α and β are the roots of equation 4x^2 - 2x - 1 = 0, find α - β

2. RadEn

use formula : α - β = | (sqrt(D)/a) | with D=b^2-4ac

3. apple_pi

oh yeah... forgot to put - without finding the roots So like using αβ = c/a and α+β=-b/a

4. RadEn

right, but ur problem to find value of α - β?

5. apple_pi

yes. find α - β

6. RadEn

we know that general form of a quadratic equation is ax^2+bx+c=0 so, we can find α - β with formula : α - β = abs(sqrt(D)/a)

7. ParthKohli

You can always count on finding the roots and assuming them as $$\alpha, \beta$$.

8. ParthKohli

$x = {2 \pm \sqrt{4 - 4(4)(-1)} \over 8}$

9. apple_pi

@ParthKohli, without finding roots

10. RadEn

yea, right to.. but should use absolut sign because not known α > β or α < β

11. apple_pi

yeah ok

12. RadEn

so, what ur answer ?

13. apple_pi

1.128

14. RadEn

yea, or (sqrt(5))/2 ?

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