Quadratice formula

G

Guest

Guest
quadratic formula

If x^2 - 2x - 1 = 0, then x =

I am stuck, can someone help?
 
So you're saying it is 3 1/2? That isn't right. Show your steps.
 
sorry I guess I typed it wrong

x^2-2x-1=0

x= -2 +/- square root 2^2-4 x 1 x 1 / 2 x 1

1 +/- 3 1/2
 
You're not far off, Baseballpro.

Just be careful with your signs.

First compare your quadratic equation

\(\displaystyle \mbox{ x^2 - 2x - 1 = 0}\)

with

\(\displaystyle \mbox{ ax^2 + bx + c = 0}\)

So we have:

\(\displaystyle \mbox{ a = 1 }\) (you're good)
\(\displaystyle \mbox{ b = -2 }\) (the negative is attached)
\(\displaystyle \mbox{ c = -1 }\) (again, don't forget the negative sign)

Now plug these into the quadratic formula

\(\displaystyle \mbox{ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}}\)

to have:

\(\displaystyle \mbox{ x = \frac{-(-2) \pm \sqrt{(-2)^2 - (4)(1)(-1)}}{2(1)}}\)

Be careful with the signs to simplify:

\(\displaystyle \mbox{ x = \frac{2 \pm \sqrt{4 - (-4)}}{2}}\)

And continue.
 
1 +/- 2^(1/2) is correct, Mandy.

Now let Baseballpro arrive at that.
 
You must log in or register to reply here.
Top