about those quadratic equations......

[Molly]

hello again.....wow those quadratic equations are something huh! I have this question in my text book that asks to compleat the square for the following: x^2 -6x-2. It seems simple enough to do by decomposition, but my teacher wanted us to express the roots by using the quadratic equation. Anywho, I did that, and I got an answer of x=6.3 and x=-1.2. I thought everthing was fine and dandy until she tells us that the roots are in fact 6.3 and 0.3??????? any help in solving this mystery would be nice....I've tried many a time with no cigar to show! Thanks....Molly :wink:

 

[daon]

Using the Quadratic formula you get:

\(\displaystyle \frac{6 + 6.6332}{2}\) and \(\displaystyle \frac{6 - 6.6332}{2}\)

 

[Molly]

hey thanks...i appreciate the answer!.....If i could trouble you further on how exactly you got that, it would be great....sorry, Im a really slow learner.....Molly :lol:

 

[galactus]

All you do is plug your coefficients into the equation.

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

a=1, b=-6 and c=-2

Don't let the negatives trip you up. i.e., -b=-(-6)=6

 

[daon]

hey thanks...i appreciate the answer!.....If i could trouble you further on how exactly you got that, it would be great....sorry, Im a really slow learner.....Molly :lol:

How did you get +6.3 as an answer if you don't know how I got what I did in my post? As galactus said, I used the quadratic equation with a = 1, b=-6, c=-2. If you take it step by step you will arrive at the point that I showed in my post. I got the 6.6332 by the square root of 44. 44 came from \(\displaystyle b^2 - 4(a)(c)\). Hope that helps.