• Oct 7th 2009, 10:43 PM
olivia59
When using the quadratic formula, if the coefficient of x squared is negative does that mean a is negative or absolute?
• Oct 7th 2009, 11:11 PM
earboth
Quote:

Originally Posted by olivia59
When using the quadratic formula, if the coefficient of x squared is negative does that mean a is negative or absolute?

Of course a is negative.

Here is an example:

Solve for x:

$\displaystyle -3x^2+21x-30=0$ Using the quadratic formula:

$\displaystyle x=\dfrac{-21 \pm \sqrt{21^2-4 \cdot (-3) \cdot (-30)}}{2 \cdot (-3)}$

yields

$\displaystyle x=2~\vee~x=5$
• Oct 8th 2009, 12:00 AM
pacman
When using the quadratic formula, if the coefficient of x squared is negative does that mean a is negative or absolute?

ax^2 + bx + c = 0 is the quadratic equation. The coefficient of x^2 which is a can be positive or negative.

-2x^2 + x + 3 = 2x^2 - x - 3 = 0, but in case you have this -2x^2 + x + 3 = 0, using quadratic formula, a = -2. But if you choose 2x^2 - x - 3 = 0, then a = 2.
• Oct 8th 2009, 04:56 AM
stapel
Quote:

Originally Posted by olivia59
When using the quadratic formula, if the coefficient of x squared is negative does that mean a is negative or absolute?

If $\displaystyle a$ is negative, then $\displaystyle a$ is negative. (Wink)