# roots of equation

• Aug 20th 2007, 01:53 PM
gregorio
roots of equation
if i am asked roots of equation for ax^2+bx+c=0 which formula is this, it may seem easy but i not sure what asking
• Aug 20th 2007, 02:08 PM
ThePerfectHacker
Quote:

Originally Posted by gregorio
if i am asked roots of equation for ax^2+bx+c=0 which formula is this, it may seem easy but i not sure what asking

If $\displaystyle a\not = 0$ and let $\displaystyle \Delta = b^2 - 4ac$.

If $\displaystyle \Delta >0$ the roots are $\displaystyle \frac{-b+\sqrt{\Delta}}{2a},\frac{-b-\sqrt{\Delta}}{2a}$

If $\displaystyle \Delta = 0$ there is just one root $\displaystyle -\frac{b}{2a}$

If $\displaystyle \Delta < 0$ the roots are $\displaystyle \frac{-b+i\sqrt{-\Delta}}{2a}, \frac{-b-i\sqrt{-\Delta}}{2a}$. Where $\displaystyle i$ is defined to be so that $\displaystyle i^2 = -1$.
• Aug 20th 2007, 08:25 PM
CaptainBlack
Quote:

Originally Posted by gregorio
if i am asked roots of equation for ax^2+bx+c=0 which formula is this, it may seem easy but i not sure what asking

You should use the quadratic formula for the roots.

RonL
• Aug 21st 2007, 06:16 AM
topsquark
Quote:

Originally Posted by gregorio
if i am asked roots of equation for ax^2+bx+c=0 which formula is this, it may seem easy but i not sure what asking

Or, if you want some practice, you can solve this using the completing the square method. The final answer is the quadratic formula.

-Dan