# Equation help!!!!!

• November 13th 2007, 12:49 PM
midnightskate3
Equation help!!!!!
how do u find the roots of the equation 2xsquared+7x-1=0
• November 13th 2007, 01:57 PM
Jhevon
Quote:

Originally Posted by midnightskate3
how do u find the roots of the equation 2xsquared+7x-1=0

for a quadratic of the form $y = ax^2 + bx + c$, the roots are given by:

$x = \frac {-b \pm \sqrt{b^2 - 4ac}}{2a}$
• November 13th 2007, 02:39 PM
topsquark
Quote:

Originally Posted by midnightskate3
how do u find the roots of the equation 2xsquared+7x-1=0

Or you can complete the square:
$2x^2 + 7x - 1 = 0$

$2x^2 + 7x = 1$

$2 \left ( x^2 + \frac{7}{2} \right ) = 1$

$2 \left ( x^2 + \frac{7}{2} + \frac{49}{4} \right ) = 1 + 2 \cdot \frac{49}{4}$

$2 \left ( x + \frac{7}{2} \right ) ^2 = \frac{51}{2}$

$\left ( x + \frac{7}{2} \right ) ^2 = \frac{51}{4}$

$x + \frac{7}{2} = \pm \sqrt{\frac{51}{4}}$

$x = -\frac{7}{2} + \pm \frac{\sqrt{51}}{2}$

(If you want more details, just ask. :) )

-Dan